The same topic keeps coming up at ranges, pro shops, and on archery forums. Someone asks which thumb button release to get. The responses are usually "Stans run small, go one size up from the UV Button," or "Carters fit most people, unless they don't," or "just try them at a dealer." That's great advice, if your buddy has a bunch you can try out or if your local pro shop actually stocks multiple makes and the full size range. Most don't. This guide gives you actual numbers.
The Onnex comes in four configurations: Thumb, Hinge, Resistance, and Clicker. All four share the same handle, hook placement, and point of impact. If a Large Onnex Thumb fits your hand, a Large Onnex Hinge fits identically. The configuration only changes how the release fires. The Clicker adds an audible click mechanism co-developed with Joel Turner of Shot IQ, dimensionally identical to the standard Thumb.
Sizes run Small through XXL, five options. Most releases come in one size, or at best two.
The finger configuration is adjustable on the same release. Swap the finger extension with a single 5/64" Allen key screw and the release shoots as 2-finger, 3-finger, or 4-finger.
At $290-320, the Onnex is priced above Carter's lineup (and just below the UV Button). The gap comes down to six things.
Independently measured dimensions for all five sizes:
| Size | Head length | Overall length (3-finger) | Span (1→2) | Span (2→3) | Span (3→4) |
|---|---|---|---|---|---|
| Small | 1.38" | 3.41" | 1.22" | 0.80" | — |
| Medium | 1.50" | 3.64" | 1.33" | 0.80" | — |
| Large | 1.50" | 3.75" | 1.38" | 0.95" | — |
| XL | 1.62" | 4.09" | 1.38" | 1.00" | — |
| XXL | 1.75" | 4.32" | 1.43" | 1.05" | — |
Head length is measured from the bottom of the first finger groove to the top of the hook assembly. Finger span is measured between groove bottoms along the axis your fingers stack. The 3→4 span applies only when the optional 4-finger extension is installed.
Two measurements. The first determines release size. The second determines head length compatibility.
Between sizes, go up. A slightly roomy fit is manageable; a tight fit causes inconsistency at anchor.
This is the distance your finger spans along the release head between the hook and the first groove. Archers with a measurement under 1.25" will definitely feel that extra head length at anchor. Coming from a Carter Too Simple, expect to lose roughly half an inch of effective draw length (around 5 fps); some archers lose closer to a full inch depending on anchor position.
Head length also affects peep height. A 0.12" difference shifts your anchor point enough to require a peep adjustment. Set your peep on the new release before hunting with it.
| Release | Head length | Overall (3-finger) | Span (1→2) | Span (2→3) |
|---|---|---|---|---|
| Carter Too Simple | 1.00" | 3.83" | 1.40" | 1.10" |
| Carter Wise Choice | 1.25" | 3.83" | 1.40" | 1.10" |
| Stan Onnex Large | 1.50" | 3.75" | 1.38" | 0.95" |
| Stan Onnex XL | 1.62" | 4.09" | 1.38" | 1.00" |
| UV Button (gen 1, Medium) | 1.88" | 3.75" | 1.5" | 1.25" |
| UV Button 2 (gen 2, Standard) | 1.65" | 3.75" | 1.45" | 1.20" |
The common AT guidance, "if your Carter fits, go Large Onnex," holds up. The Wise Choice at 1.25" and the Onnex Large at 1.50" are close enough that most archers transition without adjusting peep height. Moving from a Carter to an Onnex XL, or from a Nock 2 It to any Onnex, will likely require a peep adjustment.
The Onnex adds five sizes to Carter's one, modular 2/3/4-finger configuration on a single release, 30-degree sweep adjustment, multi-axis barrel position, spring-loaded hook, melonite-coated sear, and a trainer lock pin. Carter's 3-finger and 4-finger releases are separate products at separate prices; on the Onnex you swap a finger extension with an Allen key.
The Too Simple's shorter head length is a real advantage for short-draw archers; see the head length section above for the draw length implications.
The Carter 24-series (Too Simple 24, Wise Choice 24, First Choice 24) are 2024 products with a redesigned trigger, not year-tagged versions of the originals. Sizing relationship is the same: Wise Choice 24 shooters map to Onnex Large, Too Simple 24 shooters should account for the head length difference.
The UV Button 2 shortened the neck roughly 20% from the original, recovering about a quarter inch of draw length. At 1.65" it still runs longer than the Onnex Large at 1.50". Archers shooting a UV Button Medium in either generation typically need an Onnex Large, not an Onnex Medium.
The UV Button has fewer adjustment variables, no sweep adjustment, fixed barrel position, and two sizes vs five. For archers who want to pick it up and shoot with minimal tuning, that's simpler. For archers with unusual grip geometry, the Onnex adjustment range covers more ground.
These are different trigger philosophies. The HBC fires when thumb pressure reaches a set threshold, somewhat independently of deliberate activation. It suits archers who load into the back wall and let the shot build. The Onnex fires on deliberate thumb activation with defined travel and tension. Choose based on how you want to execute the shot.
Carter releases come in one size; most Carter shooters land on a Stan Large. Coming from a large from most other brands, likely XL. Depends heavily on finger proportions, but it's the right starting point.
The SX3, Perfex, and Onnex all share the same finger bed dimensions at equivalent sizes. If you shot a Perfex Large and it fit, the Onnex Large should fit you identically.
The Onnex ships in standard aluminum and Heavy Metal brass. The brass version is roughly twice the mass (200-220g vs 100-110g). Experienced target archers overwhelmingly prefer it.
A heavier release dampens the micro-movements that happen at the moment of firing. With a light release, small variations in thumb pressure or hand tension translate more directly into shot variation. For target shooting and TAC-style courses where every bit of accuracy counts, Heavy Metal is the better choice.
For bowhunting, most hunters won't notice the weight difference either way. It comes down to preference and the $30 price delta. If you hunt and compete, Heavy Metal is the easy call.
Once size is right, the adjustment variables are sweep angle, barrel post length, barrel diameter, and lateral barrel alignment. The Onnex gives you independent control over all four.
The finger extensions have a 30-degree range of sweep adjustment. This controls the angle at which your fingers wrap the handle. Archers with a more aggressive forward grip angle need more sweep; archers with a relaxed, flatter grip need less. The sweep is also a fit compensator: if you're between sizes, adjusting sweep can close the gap between what the dimensions say and what feels right in your hand.
The release ships with two barrel post lengths and two barrel diameters, four possible combinations:
| Small barrel (7/16" dia) | Large barrel (5/8" dia) | |
|---|---|---|
| Short post (1") | 1" | 1" |
| Long post (1.25") | 1.25" | 1.25" |
Post length controls how far the barrel sits from the back of the handle. Long post suits archers with a longer thumb, wider palm, or more extended grip angle; short post suits a more compact grip. Barrel diameter controls the contact geometry your thumb works against. The difference between small and large is the difference between a defined point-contact trigger feel (7/16") on the bones in the inside of your thumb knuckle, and a broader pad-contact feel (5/8").
The barrel needs to sit inline with the spine of your release, not canted to one side. When offset laterally, your thumb applies rotational force at the shot rather than pure rearward pressure, which introduces inconsistent downward torque into the string. On most releases, barrels have limited adjustment and you adapt your grip to the release. On the Onnex, the post can rotate and cant on four different axes independently from the handle axis. You adapt the release to your ideal grip and anchor point.
Setup sequence: size first, then sweep to match your natural grip angle, then barrel height so your thumb contacts the barrel at full draw, then fine-tune the lateral rotation of the post until the barrel aligns with your thumb's natural push axis. Replace the button-head screws with socket heads before you lock everything down.
If you're on a Carter or another release with an offset barrel position, Vernie Broyles (@exokiecustomknobs) makes aftermarket brass center-cut buttons that bring the barrel inline with the spine of the release for ones that don't offer center-cut with multi-axis adjustment. Worth knowing about if you're not ready to switch.
Sizing is only part of the decision. Our release selector covers every thumb button release on the market. It evaluates your hand size, draw length, hunting setup, and execution style to tell you exactly where the Onnex ranks for your specific setup, and what else is worth considering.
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