: Ok, now I know where I've seen them, West brand epoxy sells them,
: $3 each.

Apparently they are used for applying epoxy. Great minds think alike--or at least steal ideas from each other :)

Mcmaster Carr sells reloadable, and reusable caulking equipment ( the tube with an attached handle ) that is used when caulking compounds are purchased in bulk. The format of their images on their website doesn't work with this Bulletin board, so i can't link to the illustration, but the webpage of their caulking products is:
http://www.mcmaster.com/#caulk-tube-caps/=bb0ylx, or you can go to their homepage and search for "bulk-load caulk guns"
PGJ