To use a socket in common, regardless of a faucet type for the use thereof by providing a large diameter cylindrical part mounted on a faucet delivery pipe, with one end screwed and fixed thereto, and a small diameter cylindrical part concentrically laid on the other axial end of the large diameter cylindrical part and formed to have a threaded part on the external surface thereof.

When the external surface of a delivery pipe 51 has no threaded part, both of a socket 2 and a nipple 3 are used. In this case, the socket 2 is externally coupled to the delivery pipe 51 of a faucet 50 via an intermediate ring 5, and secured with set screws 6 at peripheral four positions. Thereafter, nut members 62 are tightened and a seal ring (large) 4 is compressed with a sharp rib 3d formed on the end of the nipple 3 and the delivery pipe 51, thereby keeping the water passages of the faucet 50 and the nipple 3 communicated to each other in a watertight state. When the external surface of the delivery pope 51 has a threaded part, only the nipple 3 is used. In this case, the nut members 62 tighten and secure the nipple 3 to the threaded part of the delivery pipe 51. The large diameter stepped part of the nipple 3 and a stopper ring 7 compress a seal ring (small) 8, thereby keeping the water passages of the faucet 50 and the nipple 3 communicated to each other in a watertight state.