The Model 437 Heavy-Duty Head is a rugged fixturing Head for heavy-duty projects. The Head is recommended to be used with the Model 400 Heavy Duty Base. Equipped with four "Universal" slots 0.29" wide for attaching forms, parts, ect. The flat head is 3" x 6" and has a 1" diameter shaft that is 3.25" long. The shaft is drilled and tapped 1/4-20 (screw included) for permanently securing to the base.