babyboomer1001: 100% silicone is perfect caulk between a sink flange and the bottom of stone. Polyseamseal and other Latex caulks are not; they do not have the adhesive stickiness or flexibility of silicone. It's best if you can pull your sink, clean the sink flange and stone bottom, recaulk with silicone and reinstall the sink. If this isn't reasonably possible, use a stiff plastic shim or plastic laminate to gouge the caulk out, clean the gap with acetone, and recaulk with silicone. Ignoring a leaking sink flange can have catastrophic consequences if your top has been "rodded" or reinforced with steel. If the fabricator used the wrong rod and/or the wrong bedding the rod can rust and blow up your top. I've fixed about 8 of these so far and it runs around $1,000.00-$1,600.00.

There is also another GE Silicone II K/B Supreme that is "mold-free product protection helps keep the cured caulk mold- and mildew-free and looking clean for 10 years, with regular cleaning." Here is a link that might be useful: GE Silicone II K/B Supreme

We're comparing apples to oranges. Cinclips are a fine product and will be a best value to the lesser-skilled DIYer who will gladly trade ease of installation for a bit more money. For a production fabricator, it isn't even close. The significantly lower cost of the HUSH and Sink Strap (7x's less) combined with the speed that comes from experience of repeated installations, make them a better value for that buyer. As a general rule, production fabricators don't shop and review on Amazon for common supplies, unlike a homeowner with a failed sink to repair.

"1. What kind of clear silicone can I use to fill the gaps?" Any 100% clear silicone will work, but this should be done by the installers, not you. You don't want to give them the opportunity to say you screwed it up. "2. How long does it last before I have to scrape it off and re-apply?" The silicone that's doing the gasketing job it's meant to do should have been applied to the sink flange liberally enough that when the sink was clamped tightly to the bottom of the top, it squeezed out. The squeeze-out should be tooled. Any additional silicone as you are applying is topical and cosmetic in nature. Peek under your sink. If you see no silicone squeezing from the flange, have them remount your sink properly. Your top looks like estone, but in natural stone tops that have been rodded, improperly gasketed sinks can cause catastrophic rod failures which I charge $800=$1,600.00 to fix and you can usually still see the crack. "3. Is there a clear silicone with antibacterial features? The sink will be exposed to a lot of germs?" Keep it clean and it will be fine.