Adjusting Tightener Arm Length to Hole Center 1 in For Shaft Thread Size 3/8 In.-16 Includes Tightener Shaft Yes Mount Base Length 2 5/8 in Mount Base Width 5/16 in Mount Hole Diameter 1/4 in Overall Length 2.69 in Shaft Diameter 0.5 in Shaft Length 1.5 in Shaft Thread Size 3/8 In.-16 Thread Length 1/2 in Compatible Idler Pulley Grainger Part Number 6AGP0 (Flat) 6AGP4 (V-Belt) 6AGP5 (V-Belt)