The midway adapter is the red headed step child of adapters. It's in the middle, hence the name. It doesn't reflex all the way over the barrel like the OTB series but it also doesn't add full length to the barrel like the PTB series. This adapter is for people who don't have enough exposed barrel to run the OTB but don't want to add the length of the PTB. With the Midway adapter you only need 1.45" of exposed barrel MEASURED FROM BARREL SHOULDER. Barrel must fit the following parameters: 1.45" of exposed barrel measured to shoulder .75 OD or less 1/2A-28 threads