Vespel blend rotor seals have an operating pH range from 0 to 10. Tefzel blend and PEEK blend rotor seals have a pH range from 0 to 14. Strong oxidizing acids such as concentrated nitric and sulfuric are not compatible with PEEK.
Don't Risk using imitation parts. Only Genuine PerkinElmer authorized Rheodyne rotor seals confidently maintain Rheodyne Valve performance in your validated instruments.