I believe my Chicago Pneumatic is a 4x, I'll look when I get home tonight. Keep in mind, the standard aircraft rivet sets are not made to match AK rivets. I custom made my set from a chineses air hammer punch I cut off. I put it in my lathe, used a 5/16 carbide endmill to open it up a little and worked it with a dremel to finish it off. I bought a pound of steel 5/32 steel rivets and practiced some to make sure it was perfect before I shot any into a receiver.