Sale includes (4) sst manifold fitting assemblies with compression nut, o-ring insert fitting, and split ring. Four piece assembly. These compression fitting kits are for attaching 1/2" PEX tubing to several brands of plumbing and heating manifolds that have a 3/4" BSP threads(1.04" od). Note: The o-ring shaft that fits into the manifold fitting bore is .705" od