O-rings are the most important components of your underwater camera system. If the O-ring is lubricated, it will be elastic enough to shape itself uniformly around the channel providing a proper seal. If it is dry, there will be too much friction to allow it to reshape itself uniformly. It will not safeguard against flooding. Underwater Photographic Equipment cannot be Watertight unless the O-rings that Seal it are Flawless. Always carry spare O-rings in your camera case. Replacement O-rings for all Sea & Sea equipment are available in protective blister packs.Every time you open the photographic equipment to change film or batteries, examine the O-ring and service if necessary. Always clean and lubricate after every diving day. When in doubt about the sealing capability of an O-ring, always discard and replace. Never use a sharp or pointed object to remove an O-ring! Use Sea & Sea's O-ring remover tool (see SKU SSORR). Don't over grease! Too much grease attracts debris that will disrupt the seal and cause flooding. A perfectly greased O-ring looks moist and shiny.The Sea & Sea O-Ring Set for Strobes is designed as spares for the Sea & Sea YS-30 / 90 / 110a / 01 / 02 / 03 / D1 / D2 Strobes (see SKU's: SSYS03ULS, SSYS01, SSYSD2).