 One upgrade that must be bought immediately is a bottom line setup, the most popular of these being an on/off valve style ASA (Air Source Adaptor) with a macroline hose.Any 45 style grips will fit it and all Autococker/Intimidator barrels will work as well.The feedneck is threaded into the body and can be replaced with any Bushmaster-style feed neck, such as the feednecks manufactured by AKALMP, CCM and ICDU.