This is FRESH 3M VHB 4941 Adhesive. It's a double-sided, round disc, long-lasting, waterproof, and provides a super-high bond. This is NOT glue, but a foam-based adhesive. There are no layers, it's all adhesive, and once it's exposed and attached to a hard surface it bonds. Applying pressure will increase this bond, but it's best after 8-12 hours. The diameter is 19.95mm or 0.79in diameter. Available to purchase per piece or in bulk quantities. Don't buy STALE, old adhesive! We move so much of this, we guarantee freshness. To ensure a great bond, clean all surfaces using 90% Isopropyl Alcohol before applying adhesive. Do not use 'rubbing alcohol' because rubbing alcohol has oil in it that prevents adhesion. Not for use on leather, fabric, rubber, or silicone surfaces. Works well to attach belt clips on smooth TPU phone cases.