This is a new made grease gun magazine well and will accept Grease GUN .45 ACP magazines.  It is designed to work with tubes with an outside diameter of 1.5" to 1.81" (original OD).  It is ready to fit a 1.5" OD tube as is.  To fit an original 1.81" tube, the top has lines etched where it needs to be trimmed off.  A STEN release button will fit if modified and other parts are fabricated.  This does NOT come with modification instructions.  Welding and hand fitting is required for installation.