31mm mounts for U.S. Squares & Semi Jumbo, 25 pieces per pack. Hawid mounts are made from pure polystyrene without harmful additives like softeners. The archival qualities of Hawid mounts have been well established with over 55 years of experience. Hawid mounts give permanent protection and also enhance the beauty of your collection. Hawid mounts are the mount of choice for many post offices and government agencies worldwide. Available with black or clear background, choose above.