Professional Repair Grade: 3-Layer Composite Adhesive for S21 Ultra Restore your phone's integrity with our industrial-strength back cover adhesive. Unlike standard single-layer stickers, our product is engineered with a triple-layer "sandwich" structure designed specifically for the rigors of mobile repair. Why Choose Our 3-Layer Structure? White High-Tack Layer: Formulated to grip the micro-textures of the metal frame for maximum adhesion. Black PE Foam Core: Provides essential shock absorption to protect the rear glass and acts as a closed-cell barrier against dust and moisture. Black Glass-Bonding Layer: Optimized for a smooth, flush finish with the glass back panel, ensuring a clean, factory-like appearance. Precision Pre-Cut for Hassle-Free DIY Skip the frustration of manual trimming. Each sticker is precisely machine-cut to match the internal contours of the Samsung Galaxy S21 Ultra (SM-G998U/G998U1/G998). This ensures: Zero Overhang: No messy glue leaking from the edges. Perfect Alignment: Holes for cameras and sensors are accurately positioned. Beginner Friendly: Makes the repair process faster and significantly reduces the risk of error. The Truth About Water Resistance We believe in being honest with our customers: While our adhesive material is designed for sealing, achieving a waterproof result depends 100% on the quality of installation. To get the best possible seal, you must: Thoroughly Clean: Remove every bit of old adhesive residue using 90%+ isopropyl alcohol. Ensure Flush Fit: Verify the frame is not bent and the back glass sits perfectly flat. Apply Pressure: After sticking, apply firm, even pressure for at least 30 seconds to fully activate the bond. What's in the Box? 2 x Pre-Cut Back Battery Door Adhesives (A spare is included for your peace of mind).