Post-1975: This is an inside magazine tube for the Marlin model 60, 99C, & 990 rifles. It replaces Marlin part number 507522. It is 20 7/8" from the tip of the knurling to the end of the tube and 22 1/8" overall. It fits serial numbers that begin with 11 and go through 25. Mfg: The Gun Garage SPECS: Made for post 1975, model 60.