Hermetically sealed, ideal for high corrosion resistance.No metal to metal contact, ideal for cleanroom applications.Strong magnetic force.Optional counter plate: Stainless Steel MC JM49, AS 68, Plastic Sealed MC JMP4WARNING: This product can expose you to chemicals including carbon black, which is known to the State of California to cause cancer. For more information go to www.P65WARNINGs.ca.gov.