This Olympus front o-ring is for the PPO-02 underwater protective case (lens port). This lens port is for use with the Olympus WCON-07C wide angle lens when used in the underwater housing PT-020. The housing PT-020 is for the Olympus C-5060 Camera. The o-ring resembling a thick rubber band is designed to establish a watertight seal when going underwater.
Manufactured to precision tolerances required to hold a pressure seal on your housing and made of elastomeric material, it provides the means by which a watertight seal is formed.