A fiberglass hole plug for sealing unused openings in electrical enclosures is disclosed. The hole plug includes a cover having a first side and a second side and defining a peripheral edge and a threaded member having a first end and a second end. The second end of the threaded member is attached to the second side of the cover, axially extends in a direction away from the cover, wherein a radial distance between the threaded member and the peripheral edge on the second side of said cover is less than or equal to one-half inch. The hole plug further includes a fastener threadably attached to the threaded member, whereby rotation of the fastener adjusts a longitudinal distance between the first end and the second end of the threaded member.