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 1/4 inch, 30 mm base diameter: 3/8 inch, 9.5 mm material: nickel plaque finish: Silver nickel color: Silver screw type: inch #8-32 x 3/8″ length thread shape: standard tree Bag size: 20 spikes