News·26 September 2026·2 min read
Srixon's Z-Star Diamond Passed All 36 Balls in Ball Lab — and Still Only Scored 89
A perfect defect record, a B- for compression consistency, and a $54.99* (£41.49) price that has to answer for both.
MyGolfSpy has published its 2026 Ball Lab teardown of the Srixon Z-Star Diamond, and the headline number is a clean one: a Good Ball Rate of 100 percent with zero defects across all 36 balls. The final grade is less tidy — 89 out of 100, a B+, and a Conditionally Recommended verdict.
Zero defects is not the same as zero variation
Ball Lab is a manufacturing audit, not a performance test. MyGolfSpy measured weight, diameter, compression, roundness and balance across 36 balls from three boxes of the three-piece urethane Z-Star Diamond, which sits in the premium segment at $54.99* (£41.49) per dozen.
The interesting part is why a flawless defect record still lands short of an A. Every category graded between B- and B, with no standout weakness and no exceptional strength, and compression consistency — the category MyGolfSpy weights most heavily — came in at B-, which is what keeps the score down. In plain terms, a B- for compression consistency means measurable ball speed variation is possible across the sample, and weight consistency also graded B- with one outlier in Box 1 widening the spread. Compression symmetry graded B, meaning each individual ball is internally consistent; the variation is ball-to-ball, not within a ball.
Verified DataSource: MyGolfSpy.
*Converted to £ at the exchange rate on 26 September 2026, the day this article was published (US$1 = £0.75458). Prices are as reported and subject to change; the conversion was correct at the time of publishing.
Quality control and on-course fit answer different questions
None of this tells you whether the ball suits you, and it is worth keeping the two apart. Today's Golfer's 2026 robot testing rated the same model highly on the course: the Z-Star Diamond won an award in every category bar off-the-tee performance, taking gold for tee-to-green at 114mph, 93mph and 78mph, gold for approach play and gold for short game.
So you have a ball that performs strongly in independent robot testing and manufactures to a merely good, not outstanding, standard. Both things are true. A golfer paying premium money is entitled to know both before they buy three dozen.
Where this fits into a fitting
We are brand-agnostic and we do not sell balls, so we will say the unglamorous thing: a B+ manufacturing grade is not a reason to reject a ball, and a gold medal in a robot test is not a reason to play one. The Diamond's profile — highest iron spin in the Z-Star family, less impressive off the tee — is a fit question about your delivery and your approach game, not a league table. BallFIT exists to work out whether that profile matches how you actually play, then you can decide whether 89/100 at $54.99* (£41.49) is a price you are happy with.
Questions? contact@kaddieiq.com
What “Verified Data” means
The figures inside a Verified Data panel are checked against a named, public source — a retail listing, a press release, an independent test — before they are published, and we link to that source directly. They are not the same as a manufacturer’s own performance claims, which we report as claims, in the body text, until an independent test confirms them. If a number carries the badge, you can check it yourself at the source link below the panel; if it doesn’t, treat it as reported rather than verified. KaddieIQ is not paid by any equipment brand and sells no clubs or balls.