Scuba Tank Keychain. 3 Different Colors. Plastic Diving Tank Key Chains Holder with O-rings 3 colors to choose from, White, Yellow, and Pink Very detailed tank valve with a hollow tank which makes it FLOAT Makes a great gift idea for all your friends and family Measures 2 1/2 inches long and 3/4 of an inch wide At the bottom of the keychain there are two of the most common O-rings used in scuba diving. Standard Yoke Regulator (AS-568-014) and Standard DIN Regulator Valve (AS-568-112 NBR), both 70 shore. You will always have a spare with you.