Ikelite 6970.03 Instruction Manual page 13

1. To attach the Lens Port, lightly lubricate the Port Base O-ring.
When properly lubricated, the O-ring should have an even, slightly
shiny appearance. Wipe off any excess lubricant. Lubricant
prevents the o-ring from rolling or extruding; it is not a sealing
mechanism. Use ONLY Ikelite lubricant.
O-ring
Thumb Screw
Zoom Gear
Port Base
13