What is the o ring on a push fit plastic fitting made of?

The O-ring on a push-fit plastic fitting is typically made of rubber or a synthetic elastomer, such as EPDM (ethylene propylene diene monomer) or Nitrile (Buna-N). These materials are chosen for their flexibility, durability, and resistance to water, chemicals, and temperature changes, ensuring a secure seal to prevent leaks. The specific material may vary depending on the application and the substances being transported through the fitting.