3/8″ copper tube size, stackable quick connect elbow, allows quick connect connection without cutting small pieces of pipe, holds up to 250 psi, 1 piece, no parts to assemble or lose, code approved for behind wall without access & direct in ground burial installations, nsf-14, nsf-61, csa/astm & upc code listed & approved, replacement for qest & flare it type fittings.