I don't know the measurement but it is flush with the base of the inset/countersink (???) for the screw in the trigger guard. Whatever that thickness is, is the amount the stand off spacer sticks through the stock. The spacer contacts the base of the action, it's seated correctly and it pokes through on the OEM trigger guard. Maybe they had an issue with the screw smashing and cracking the guard, so changed the design. This is only a guess based on the rifle sitting in front of me.