The dowel reducer on the top of the round bar provides the proper size of the dowel to ensure that the luminaire has a suitable fit. These tenons are made of sturdy steel pipes and are double welded to allow powder coating or galvanizing. Recommended for concrete, steel and aluminum rods. Custom sizes can also be manufactured for specific applications. Comes with the installed hardware. 4" round rod bracket, carbon steel, bright bronze/base: 4 screw holes for 3/8"-16/tenon: 1x vertical tenon, OD60 x HT4"