Sorry - the 'feel' doesn't come through in the picture. I'm not sure exactly what the board is but maybe as it is for development purposes, those are just 'non slip' boots to stop it drifting around the work bench.
No worries. Here's another picture (ignore the fact that the top looks a little funny; I think the cut has left it a little warped).
Hopefully the "sealed" end is displayed clearly and you can see the solid rubber part at the end that is able to absorb the shock.
I wasn't even thinking about the dual purpose, but I'd say you're right about the non-slip function. Who knows... that's probably the primary function.
Not actually rubber, either silicone "rubber" or a different plastic elastomer.
No idea why your board would "bounce"? Has it a motor or other vibrating device?
In any case, it seems like you answered the question yourself. This are simple pieces of silicone tube (or a similar material), simply cut from the reel. If you plan to use more than a thousand, you may want to order it as blanc cut from the manufacturer or a reseller.
The "rubber" material could be anything. As you can probably tell, I'm not all that knowledgeable when it comes to materials.
As for why it bounces, there's no mechanical device attached, but whenever I move the board, I'd rather have it standing on something springy than just having it drop with a thump on the table.
It's not for the times I place it normally, it's for if I accidentally drop it a few inches.
I'm probably just being overprotective, but I still think they're a simple product that probably cost ~0.05c each, so why not put them on every board that uses stand-offs.
Buying in bulk is always the key. :grin:
My bench isn't anti-static.... yet.
I might look into changing that. I've seen some good guides for that on the EEVBlog.
I've used "screw on" rubber feet for stand-offs in the past (see below), but these slip-on ones seem much simpler. And better.