Fits my R51 pneumatic stapler but not strong enough to glue thin veneer to aluminum tube frame in my van's dining area. I removed the veneer as part of a renovation and found that it was glued in at the factory. I cautiously bought the same size staples to reattach the veneer to the square aluminum tube, but found that the staple legs were curved rather than penetrating the aluminum like the factory staples did. I am not satisfied. This is pack and size #2 of four different packs I have purchased. None of them pierced the square tube holding the veneer.