They only have shoulders on the inside. I got this idea from the Polaris NX, which was the reproduction version of the Colt in 71. I basically had the Colt tooth put on the NX driver. There is no need for a shoulder on both sides, and less material makes a less expensive part. I include all the hardware needed to install them as well. I also am now including NOS snap ring 7713901 in the hardware kits.