Mizuno RB 566 Review (2026): How It Compares to the RB Max, Pro S and Pro X

Quick answer

Mizuno’s four balls at a glance

Compression figures come from BallCaddie’s ball catalog. Prices were verified on Mizuno’s US store in September 2026. The “robot-tested” column refers to MyGolfSpy’s 2026 48-ball test, the largest independent robot field published this year. That test ran three driver conditions at 116, 102 and 86 mph of swing speed, and three iron conditions at 90, 80 and 65 mph, so every ranking below belongs to a specific club at a specific speed.

Why Mizuno’s own comparison chart won’t pick for you

Mizuno grades all four balls on five sliders: feel, compression, trajectory, short-game spin, and driver spin. On Mizuno’s own US product page, the Pro S and Pro X land on the same trajectory rating (Medium) and the same short-game spin rating (High). Only three of the five sliders separate them at all: feel, compression, and driver spin.

The page then contradicts its own table. The slider says the Pro X trajectory is Medium, while the feature copy directly below says the Pro X “is designed to produce a higher trajectory, ideal for players seeking greater apex height and a steeper landing angle on the greens.” Both statements are on the same page.

Measurement settles it. At MyGolfSpy’s high swing speed driver condition, the Pro X peaked above 91 feet, more than five feet above the test median, alongside the Titleist Pro V1x (~102) and Snell PR4 (~89). The feature copy was right and the slider was wrong.

Mizuno Pro X: seventh off the driver, 47th off the iron

The most quoted number in the 2026 test belongs to the Pro X. Within the mid swing speed group it ranked seventh of 48 for driver ball speed and 47th of 48 for 7-iron ball speed — the driver condition at 102 mph, the iron at 80 mph. MyGolfSpy used it to make a point about the field, noting the Pro X was slower off the iron than a $15 Amazon Basics Core Soft (~55).

Read the second half of that carefully, because MyGolfSpy immediately defuses it. The entire 48-ball iron field was covered by less than 1.5 mph, with 18 balls in a statistical tie at the top, and the test’s own conclusion was that “ball speed off irons shouldn’t be a major concern when choosing a ball, at least not in isolation.” Forty-seventh sounds like lost yardage and mostly isn’t; our read of the full 2026 test covers why iron distance tracks spin far more closely than it tracks speed.

The finding that should actually move you is driver spin. Mizuno’s chart grades the Pro X at Medium. MyGolfSpy put it among the highest-spinning balls off the driver at mid swing speed, with only the Srixon Z-Star Diamond (~93) and Callaway Chrome Tour X (~99) in the same group, and it sat just behind the leaders again at the 86 mph condition. The test named it a high-spin top pick at mid swing speed, sharing that slot with the Pro V1x and Vice Pro Plus (~97).

Pair that with the 91-foot apex and the Pro X becomes a specific fit: a player who wants a high window and a steep landing angle into greens. A golfer already fighting a ballooning drive should read “among the highest-spinning off the driver” as a warning rather than a feature, whatever the Medium label says.

Mizuno Pro S: the more complete ball of the two

The Pro S took a low-spin top pick at high swing speed, sharing the category with the Titleist Pro V1 (~92) and TaylorMade Tour Response (~74). Mizuno’s own low driver-spin rating for this ball holds up under measurement, which is worth saying plainly given how often stated specs miss.

Off irons the Pro S behaved unusually well for a firm ball. At high swing speed MyGolfSpy named it one of the three longest firm options, with the Chrome Tour Triple Diamond and Maxfli Tour X, in a section where the test noted that firm balls normally fall off and softer models rise to the top. Its iron spin sat in the bottom half of that chart despite the firmness.

The result that should change minds arrived at the slowest condition. At the 86 mph driver setting, the Pro S finished third for total distance in the 48-ball field, behind only the Pro V1 and Titleist Tour Soft (~88), with the top five separated by about a yard. A 96-compression urethane tour ball has no business being that long at 86 mph under the usual rules, and the compression chart explains why the soft-is-longer assumption breaks down more often than ball marketing admits.

The Pro S does sit at the wrong end of one chart. Off the 65 mph iron it was among the slowest in the field, with the Maxfli Tour X LS (~97), Snell PR3 (~91) and Z-Star Diamond, all firm urethane models. MyGolfSpy’s caveat applies here too: that whole field was separated by 1.3 mph, with 12 balls tied at the top, so the balls at the bottom were barely slower than the ones above them.

Mizuno RB Max: a bridge ball with no independent data

The RB Max is a three-piece ionomer ball around 80 compression at $30, and Mizuno positions it between the value RB 566 and the urethane Pro balls. Its core is the design story: a soft inner core wrapped in a firmer outer core, borrowing construction from Mizuno’s tour balls but keeping a durable ionomer cover and 336 AXIALFLOW dimples.

Mizuno’s director of research and development, David Llewellyn, framed the target audience for Golf Digest at launch: “The RB Max is for every amateur player who likes the speed and flight control of a tour-type ball, with increased durability. Plenty of amateurs with good clubhead speed will see better results from a slightly firmer ball.”

No robot test has checked that claim. The RB Max was absent from MyGolfSpy’s 2026 field, and no published gauge reading or launch-monitor dataset exists for it from an independent lab. The cover is the certain part: ionomer gives up meaningful greenside spin against urethane, and the urethane vs ionomer breakdown puts real numbers on that gap.

Mizuno RB 566: soft, cheap, and unverified

The RB 566 is the cheapest ball Mizuno sells at $22 a dozen, a two-piece ionomer design around 60 compression. Its signature is the dimple pattern the ball is named for: 566 micro-dimples, small dimples set inside and between the larger ones, meant to hold carry when there isn’t much ball speed to work with.

Llewellyn’s explanation of the trade-off is unusually candid for a manufacturer: “With a softer ball, feel is a priority and aerodynamics become the key to maintaining distance. We’ve found that at lower swing speeds, the higher, straighter flight and impact of the smaller dimples outweigh any minor loss of ball speed of a harder ball.” He is conceding ball speed and arguing that flight recovers it.

That argument has never been checked by an independent robot. The RB 566 wasn’t in the 2026 MyGolfSpy field, Golf Monthly’s review of it dates to November 2022 and sits behind a login wall, and no calibrated compression reading has been published anywhere we could verify. The ~60 in our catalog is a placement against balls that have been gauged, and no gauge reading of its own backs it up.

One thing is settled. The RB 566 isn’t discontinued: it remains on Mizuno’s official US lineup page and in stock on Mizuno’s store at $22, checked September 2026. Its product URL still carries a 2024 model tag, so it’s an ageing ball that’s still on the shelf.

What the evidence supports

Two of Mizuno’s four balls have independent robot data. Two don’t. That split should drive how much confidence you place in any recommendation, including ours.

• The Pro X and Pro S are measured quantities. Both appeared in a 48-ball field with published rankings across three swing speeds and two clubs. You can check the claims.
• The RB Max and RB 566 rest on manufacturer design logic. Mizuno’s engineering explanation for both is coherent and specific, and it’s still the manufacturer’s own account. Independent labs skipped them.
• Price isn’t the reason they were skipped. The $15 Amazon Basics, the Callaway Supersoft (~49) and the Titleist TruFeel (~70) all made the 2026 field. Absence reflects how the field was picked.
• Mizuno’s compression labels understate both tour balls. Mizuno calls the Pro S “Medium” compression; the catalog places it at ~96. Anything in the mid-90s is firm by any tier definition, which our swing-speed framework sets at 90 and above.

Which Mizuno should you buy?

Pick by driver spin and flight, since that’s where the measured data separates the two tour balls.

Buy the Pro S if you want one ball that does most things and you swing above roughly 95 mph. It won a low-spin top pick at high speed, was named one of the three longest firm balls off high-speed irons, and still placed third for driver distance at 86 mph. It’s the most defensible $50 in the lineup.

Buy the Pro X if you need height and a steeper landing angle into greens and you aren’t already spinning your driver too much. It was seventh of 48 for driver ball speed and among the highest for driver spin, and it peaked more than five feet above the field median.

Buy the RB Max if you want three-piece construction and a durable cover at $30 and you accept that no independent lab has tested it.

Buy the RB 566 if you swing slower, want soft feel, and $22 is the point. Take Mizuno’s carry claim as a reasonable design argument that no lab has checked.

At $50, the Pro balls sit about $8 under a Pro V1x while carrying the same urethane cover and a similar compression. Whether the discount is worth trading Titleist’s in-house quality control and tour record is a judgement call, and the Mizuno lineup guide covers that brand-level comparison in more depth.

The next step

Ball choice comes down to your swing speed, your typical miss, and where your strokes go. Run those inputs through the BallCaddie fitting quiz and it scores the full ball catalog against your profile in about 90 seconds, Mizuno included. Sign up to see your match, and it’ll tell you when a $22 dozen is the right answer.

For deeper dives on the data behind this review:

• Mizuno golf balls: the complete lineup guide — the brand-level view of all four balls, how Mizuno’s contract manufacturing works, and the Pro series against the Pro V1 line.
• The MyGolfSpy 2026 ball test, read as fitting criteria — why iron distance tracks spin rather than speed, and how to read a 48-ball robot field without cherry-picking.
• Golf ball compression chart — every ball’s compression on one scale, with the swing-speed tiers.
• Urethane vs ionomer covers — what the RB Max and RB 566 give up around the green, in rpm.
• How to choose a golf ball for your swing speed — the fitting framework this review’s recommendations sit on.
• Best value golf ball in 2026 — where the $22 RB 566 lands against the rest of the value tier.

Key takeaways

• The RB 566 is a $22, ~60 compression two-piece ionomer ball that no independent robot has tested. It is still current, not discontinued.
• The RB Max ($30, ~80) is also untested by any independent lab. Both value balls rest on Mizuno’s own engineering case.
• The Pro X took a high-spin top pick at mid swing speed despite Mizuno grading its driver spin as Medium, and peaked above 91 feet at high speed. Its 47th-of-48 iron ball speed reads worse than it plays: that whole field spanned under 1.5 mph.
• The Pro S is the more complete ball: a low-spin top pick at high swing speed, one of the three longest firm balls off high-speed irons, and third for driver distance at 86 mph.
• Mizuno’s five-slider comparison chart gives the two tour balls identical trajectory and short-game spin ratings, and contradicts itself on the Pro X’s flight. Independent measurement separates them on spin and apex height instead.