100% Vespel polyimide. Upper temperature limit 350 deg. C. Blank ferrule has no through hole. Use to plug fitting outlets, or drill to special size to use with your tubing. (Image shows molded indentation.) One piece design requires no back ferrule. Packaged: 3 in. x 3 in. x 1/4 in. Plastic Dial Pack; Weight: 5.7 g.