PURPOSE: To allow a water purifier to be laid between a cap nut and a faucet for tap water or the like in a short time as well as easily, and enable a single member to cope with faucets of various bores at the time of mounting the purifier on the expanded front end of the faucet via the cap nut.

CONSTITUTION: A hole 3 for inserting a faucet is axially drilled through the center of an approximately truncated cone type member body 2 having elasticity, and a plurality of notches 4 are formed peripherally on the upper section of the body 2, so as to expand from the periphery 2b of the upper surface 2a thereof toward the hole 3. In addition, a cutout section 5 radially extended along the body 2 for the cutting thereof is formed on one of the notches 4.