frontsaet og kolberor pat2 conversion kit stdFront set and piston tube, PAT2 Conversion Kit STD The front set is complete with outer barrel, gas block, flash hider, stock with mounting bracket and delta ring. The stock tube requires a short rear end on the lower receiver and a rear out pipe. The front set is prepared for mounting 4 pcs. PAT2 rail which can be purchased separately. The piston tube is designed to contain a battery.