This is a deck mounted round flanged used for a 1.5" O.D. rail or ladder It is almost always used with above ground equipment Shape is round, with a flat flange on bottom - flange has 3 mounting holes There is a threaded hole in the flange body with center bolt hole 5/8" from the top Dimensions : Outside Dia.: 3-3/8" (Bottom Mounting Flange) Outside Dia.: 1-3/8" (Top of Flange) Iinside Dia.: 1-9/16 (Top Inside) Ht. : 2-3/8" Center to center measurement between mounting holes : 2-5/16"