These are brand new thermal switches that are designed to be placed in contact with your rechargeable cells. If the battery pack gets too hot during charging these can open the charging circuit until the pack cools down. Small size (about 0.63" long x 0.11" x 0.20" excluding leads).
Brand new - Made by Pepi. These are Model # 65 (N version) metal case rated 65° C.
Sold in a package of 10.