Next topic: service of the underwater housing, you guys ever do that? 😄

I do what you guys are doing. If it ain't broke don't touch it, however, with 4 indoor cats I do make sure to inspect for cat hair :)

I've never changed my o-rings either. I have noticed that the o-rings on the Retra strobes seem to stay in the elliptical shape when you remove them from the strobe. I wonder if they will eventually require replacing over time as a result of this inelasticity? Also, I learned from you Alex, the habit of running the o-ring through my mouth. While some may find it a disgusting habit, what I like about this approach is that it's very easy to detect any grains of sand or hair with my tongue - something I wouldn't be able to do just by feeling it with my fingers.

I am pretty sure that Nauticam's grey O-rings are, indeed, silicon, too. There are different kind on mixes of silicon and Nauticam one is definitely softer than e.g. Inon one. You can use same grease for all types of silicon O-rings. The other widely used O-ring materia is then nitrile rubber and there ase differen hardness of it, too. Most common is BR70 but e.g. tank neck O-ring's hardness is BR90.

indeed, many different types of grease look the same and are called "silicone grease" including by the manufs. Using an actual silicone based grease on silicone O'rings causes swelling. The cheap silicone tubs you get at dive shops is generally silicone grease that will cause issues with silicone O'rings. Use the manufs recommended grease, or if you want to make life easy, use cristo lube or tribo lube and it will work with any O'ring and not cause problems, and can also be used on regs including nitrox clean. A good clean water soak is crucial for the non user serviceable O'rings to reduce salt crystal formation which can damage O'rings. The average dive boat or resorts camera rinse tank is not clean water after half a dozen housings have been dunked in them. better than the ocean but still not the best, especially if you will put the housing/strobe etc in long term storage. Removing user serviceable O'rings (especially buna ones that do take on a set or shape in storage more than silicone) for long term storage (more than a few months) is important. Matthew, your "loose" O ring is most likely because it has swelled because as you said you use any old silicone. Subal are black but also billed as special super soft. They may be silicone (not sure) but if a super soft buna (rubber) the softer durometers have a lower acrylonitrile level and are more prone to swelling. Keep in mind at depth the pressure at thee seal will push the grease into the O'ring material. Buna O'rings really should be replaced annually. Silicone if not used wrong lube will last much longer.

I guess I'm better safe than sorry given the cost it would be to replace a Sony A7RIV and 16-35 GM or 90mm Macro lens, I'm pretty anal with cleaning & lubricating mine especially between dive trips - but check with the company as Ikelite states NEVER lubricate their O-rings on their strobes.