This is a very tough piece to find! It is an original wooden tompion for a .56 caliber carbine. This size would mean that it would fit the Civil War era Colt Revolving Rifle. This one has been tried in a .58 caliber rifle and it is too small and is too large for the standard .50 caliber carbine. It fits perfectly in the Colt revolving rifle of .56 caliber. It isn't listed in the gun tool book which is how scarce they are. The wood is longer than the usual tompions and measures 3-7/8ths inches in length. The last picture shows how it compares to the size of a standard .58 caliber tompion. Don't miss this rare jewel.