Although conventional fluorine-containing rubber cannot easily maintain its physical characteristics against chemicals such as ethers, amines, ketones, organic solvents, acids, or alkalis, Karlez® exhibits stable physical characteristics with respect to a large majority of these chemicals. In terms of heat resistance, Karlez®, which is a type of rubber, maintains its physical characteristics even at high temperatures up to about 300℃. 0-rings made of Karlez® are used as the main 0-rings in semiconductor equipment.