Bohning's Shock Cord Knobs are a quick and easy replacement for flimsy plastic shock cord knobs. With a flat interior edge, these knobs will help prevent your cords from slipping off; giving you peace of mind and making sure your boat stays covered under most weather conditions. Installment is easy and painless, just replace your old knobs with our stainless steel and screw them in with your existing hardware! Length: .450" Top/Bottom Flare: .570"W Middle: .250"Lx.180"W Screw Hole: .245"