The NAT 6252NR tank connector or P.O.L. from equipsupply.com has many previous part numbers and they are as follows; 113818-01, 113818 01, 11381801, 1248, 34351, 5334001, 6252, 6252NR, G1630, 16433, 6433, G1629, 147777, 5334003, G1690, G1690LP, 6433NR, 113791-01, P3200, P-3200, LPA4020, 26433, 11379101. The 6252NR tank connector with O-Ring and check valve attaches to the regulator and propane tank. Since the NAT 6252NR POL fitting has the check valve (shutoff valve, excess flow valve) in it this will shut off the flow of fuel to the unit if there is a cut or rupture of the gas supply hose. The O-ring on the NAT 6252NR and/or 113818-01 from equipsupply.com helps to maintain a tight seal inside of the valve.