MPS DOT Air Bottles come in a few sizes and configurations. The 1 pound bottles are the smallest bottles that can be used with a low pressure (120-140 psi) air shifter system. The 1 pound bottles come with a billet aluminum top with two 1/8 NPT ports (fittings not included). The smaller bottles are typically used with high pressure air shift systems. Both accept the small 5/8" thread pin valve and MPS Paintball Regulator Assembly P/N 1-0367 and 1-0329.