These rubber grommets are made of quality, flexible and durable rubber material, they are of good electric resistance capability. And the rubber o rings will fit those drill holes precisely and efficiently. Essential rubber gasket rings are for cars, RV wiring jobs, marine uses, leaky faucets, hoses repairing and so on, good tools kit for repair shops, electricians, movers, handymen, plumbers, etc. Contains grommets to suit hole sizes from 6.4mm to 25.4mm.