Shortlist · Weight-stack adders
Stack adder pins with a stated pin size and limit
Two approved GymPin stack adders, one for 8 mm and one for 10 mm selector pins, with each maker-stated limit and the machine limit that comes first.
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Short answer
Two approved stack adders state their selector-pin size and a limit, and the choice comes down to your machine's pin. For an 8 mm selector pin, choose the GymPin Original in 8 mm; for a 10 mm pin, choose the KingPin, which GymPin makes in 10 mm only.[1] Either way, the machine's permitted load comes first, and GymPin says its pins do not uprate a machine.[1]
How we chose
A stack adder is on this list only if:
- The maker states the stack-end diameter and length. GymPin lists the Original's small end, which goes into the stack, as 102 mm long in 8 mm (5/16 in) or 10 mm (25/64 in).[2] A diameter tells you whether it can fit; GymPin warns against putting an 8 mm pin into a 10 mm hole and says to match the machine's original selector pin.[1]
- The maker states a limit for that model. GymPin's Original product page states 60 kg,[3] and GymPin states a 60 kg pin load rating for the KingPin.[1] For comparison, Bare Steel states 135 lb for its 10 mm pin[4] and 100 lb for its separate 8 mm pin,[5] and Torque sells a 2.5 lb magnetic adder pin listed at 2 in diameter and 3 in long.[6] Those are not approved in our catalog.
- The maker says the machine comes first. GymPin states that its products do not certify or uprate a machine, that a stronger pin does not raise the machine's rating, and that the machine's permitted load takes priority.[1]
- The product is approved in our catalog.
Both picks are GymPin's. Two products met every point on 2026-10-10, and we do not add others to fill the list.
Adder for machines with an 8 mm selector pin
GymPin The Original 2" GymPin (8 mm, Raw)
Pick it if: Owners of a machine whose existing selector pin measures 8 mm
- Why it's here
- GymPin lists the Original's stack end as 102 mm long in 8 mm or 10 mm, a 155 mm by 49.5 mm plate end for 2-inch Olympic plates, and a 60 kg maximum stated load on its product page. This listing is the 8 mm Raw version.
- Watch out
- Only for an 8 mm selector-pin hole; GymPin warns against an 8 mm pin in a 10 mm hole. The 60 kg never raises the machine's own limit, and the pin is never the selector pin. On Amazon, check that 'Ships from / Sold by' shows Amazon.com or GymPin.
- Stated load rating
- 60
- Upright size
- Not stated
- Mount hole diameter
- Not stated
- Plate bore fit
- 2 in Olympic (plate end 49.5 mm diameter)
Values are the manufacturer's specs unless marked.
Adder for machines with a 10 mm selector pin
GymPin KingPin 10mm Weight Stack Extender
Pick it if: Owners of a machine whose existing selector pin measures 10 mm
- Why it's here
- GymPin makes the KingPin in 10 mm only and states a 60 kg pin load rating for it. Its maker page, as recorded in our catalog, lists a 102 mm stack end and a 200 mm by 49.5 mm plate end for 2-inch Olympic plates.
- Watch out
- 10 mm only, so it will not suit an 8 mm machine. The longer plate end needs more clearance; check that plates clear the frame through the full movement. GymPin says not to slam the stack. On Amazon, check that 'Ships from / Sold by' shows Amazon.com or GymPin.
- Stated load rating
- 60
- Upright size
- Not stated
- Mount hole diameter
- Not stated
- Plate bore fit
- 2 in Olympic (plate end 49.5 mm diameter)
Values are the manufacturer's specs unless marked.
Before you load it
- Measure first. GymPin tells buyers to measure their existing selector pin or stack hole, because makers use different diameters across models and years.[3]
- Check clearance. GymPin advises checking that plates clear the full range of motion, and getting the owner's or maker's permission before using its pins on equipment you do not own.[3]
- Never use an adder as the selector pin. Bare Steel warns against using its stacked weight pin as a selector pin with added weight.[4]
Questions
How do I know if I need 8 mm or 10 mm?
Measure the selector pin already in your machine. GymPin says makers use different diameters across models and production years, and to match the original pin's diameter.[3][1]
Does the 60 kg rating mean my machine can take 60 kg more?
No. GymPin says its products do not certify or uprate a machine and that the machine's permitted load takes priority. See stack adders and machine load limits.[1]
Can I use the adder as my selector pin?
No. Bare Steel warns never to use its stacked weight pin as a selector pin with added weight. Treat any adder the same way: the machine's own selector pin stays in place.[4]