This Olympus o-ring is for the PPO-04 replacement standard lens port. This lens port is for the underwater housing PT-023. The housing PT-023 is for the Olympus C-8080 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.