Description They are easily applied with a screw and Phillips screwdriver. The screws are supplied with this item. Each spike has a tap on the bottom in which the screw is applied. Description and Specs: height: approx. 1 inch, 28 mm base diameter: 3/8 inch, 9.5 mm material: nickel over zinc finish: black nickel (gun metal) color: black screw type: inch 8-32, 1/4″ length thread shape: round cone Bag size: 20 spikes