Butler Creek scope caps feature polymer construction with steel hardware to protect glass on valuable optics. Flexible rubber housing and flex-fit sleeves allow for easy installation and create a water and airtight seal.Features:Fits scopes with a 35-40mm objective lens;Heavy polymer cap, rubber housing and steel hardware;Flex-fit sleeve creates watertight and airtight seal;Black and clear inserts allow customization between solid, see-thru or data disk;Open vertical or lock down flat for unobstructed view