• Practical precaution when handling costly lenses over the sink!
• Soft rubber 
• 5.5" x 4.5" oval shape

Note from Rebecca

Pretty simple and self-explanatory. I have used this for years. Embarrassed to admit how long I've used the same one, in fact. I lower the stopper in my bathroom sink and place this over it (have to lower it to prevent gaps that a lens could sneak under). Works great. 

The BEST approach is not one of these rubber things at all. It's a generous sized terry towel over your whole sink so that your lens can't accidentally strike porcelain and crack (for example). Lenses are much less likely to bounce when they hit a towel than virtually any other surface.

Me, though, lazy, and old habits die hard, so I will continue using this. I do all my lens stuff over the counter, not the sink, so mostly I'm concerned about the lens rolling down the drain if it's not covered.