Dora,

Most small vials have a screwcap with a rubber liner or a polycone liner. If the liner looks flat (not cone shaped) and is white or light tan it may be a teflon faced rubber liner. If it is cone shaped or translucent it is most likely a polyethylene liner.

Carefully remove the liner from the cap with a small flat screwdriver blade. A teflon lined cap will have 2 layers, a smooth shiny teflon layer that is thin and a thicker rubber backing. Some teflon lined caps have red teflon and white rubber. If you place a very small drop of water on the "teflon" side it should bead up and not spread out. The water should also smoothly sheet off the liner when tipped. If the water does not bead up or sheet off cleanly it is probably a rubber liner.

Most teflon lined caps are two layer because the teflon does not compress adequately by itself to fully seal a vial. The rubber backing allows a thin teflon liner to conform to the glass lip of the vial.

Teflon faced liners for small vials are common in labs but I think it is not as likely to find them at a surplus store....but this really depends. Your best bet is to go ahead and follow Chris's advice and try them. A rubber liner will discolor and probably crumble from the iodine.