1. Centering ring for ISO-KF flange KF16, KF25, KF40 & KF50
2. Cetering ring is made of Stainless steel 304
3. O-ring, Made of FKM or so-called "Viton"
4. FKM is commonly called Viton by DuPont.
FKM/Viton is good for chemical resistance.
Working temp is-26C to 200C / -15F to 400F