Door assembly,blow in combustion air. end item identification, bushing guide,tube assembly part name assigned by controlling agency, steel corrosion resisting overall material

A tubular shaped unthreaded item with or without a flange at one end designed to be inserted into a hole to reduce the inside diameter of the hole and to protect the surrounding body structure from damage resulting from stress, strain, and/or vibration. The overall length must exceed 25 percent of the outside diameter or the shortest distance between peripheral flats of the body. Includes items which are divided into two or more segments which includes 180 degrees (3.141 radians) or less of the bearing periphery. For items made of rubber, see bushing, nonmetallic. See also bearing, sleeve; bushing, tapered; spacer, sleeve; insulator, bushing; and bushing, electrical conductor. Excludes:bushing, drill, jig.