These gas blocks are designed to be used in conjunction with Allen Engineering or Ottercreek Labs suppressors. They will not work with JR Machine Solvent traps.
These give you the shortest possible configuration for mounting an AE/OCL suppressor. They are designed to be used on a 0.750" gas block journal.
Rough estimated length for various gas systems:
Rifle length - 16.56"
Mid length - 13.56"
Carbine Length - 11.56"