Cardboard 2x2 flips are the most widely used coin holders in the industry. Just insert a coin, fold over and staple. HECO brand holders are made with thinner cardboard than Cowen's brand holders (which we also sell). Some collectors and dealers prefer the thinner holders as more will fit in a box. The inside of HECO holders are lined with Mylar, the chemically most non-reactive lining available for coins. Mylar does not tear or scratch and is also the most moisture resistant film available. Mylar film is also dustproof with the lowest available permeability. Sold in bundles of 100 or cases of 5000.