Manufactured using Plastic for the packers to be waterproof and Weatherproof (No Rotting or holding water) and re-usable These Flat Packers Available in 6 various sizes which are visible with 6 different colours for ease of use when measuring spacing etc AF4F slimline tough pack Mixed bag contains all 6 sizes 1,2,3,4,5,6mm Flat packers/shims which are serated so when stacking helps to stop slipping and movement Great quick option that stands the test of time when packing windows, doors, flooring and general building and Joinery or for Just diy at home. Light weight and small means they are super handy and stops you having to over-load bags, vans or shelving etc