BT-430298 B&T BWC9 Chassis System For Sig320
AP-200691 Aimpoint sight ACRO P-2 3.5 MOA Black
Sig Sauer P320 Carry Slide
Sig Sauer P320 Fire Control Unit
The BWC9 Chassis is an unregulated item but requires your Sig P320 to be registered as an SBR with the ATF.