This heavyweight, laminated shingle is composed of a dimensionally stable non-woven glass fiber mat, which is thoroughly impregnated with stabilized waterproofing bitumen. Cambridge® HD is distinguished by its random shape-look design, unique high contrast dual band shadow coloration, and superior thermally activated shingle sealant. Colored, ceramic granules surface the top of both layers of this shingle to protect the asphalt from ultraviolet radiation. Each shingle has release tape and mineral powder applied to the underside, thus preventing any sticking in the bundle. Special algae-inhibiting granules have been added to provide long-lasting algae resistance. Suitable for application on roof slopes greater than 4:12. Underlayment is strongly recommended for slopes below 6:12. They may also be applied on low slope roofs (2:12 to 4:12) providing the deck is covered with two plies of felt or one ply of any IKO Ice & Water Protector.