Double Cylinder Deadbolt：It could be locked and unlocked by a key from outside and inside. Dualkey operation allows locking or unlocking from both sides with keys, providing enhanced anti-pick protection. ldeal for exterior doors requiring maximum security against forced entry. Universal Round Design：Classic circular deadbolt fits standard 2-1/8" door bores, complementing modern and traditional door styles. Matte black finish resists fingerprints and corrosion. Zinc Alloy Construction：Zinc alloy body and anti-drill cylinder withstand tampering and harsh weather conditions, ensuring long-lasting performance for exterior entry doors. Adjustable Installation：Fits door thicknesses 1-3/8" to 1-3/4" with adjustable 2-3/8" or 2-3/4" backset. Quick installation requires only a screwdriver, with the entire setup completed in minutes for a time-saving and cost-effective upgrade. Customer Service：Rigorously tested for home security compliance. Verify measurements before ordering to ensure proper fit, with dedicated technical support available for immediate assistance. This double-sided circular deadbolt lock features a sleek black design crafted from durable zinc alloy. Its sturdy construction ensures reliable performance while maintaining a modern aesthetic. Installation is quick and straightforward - simply use a standard screwdriver to complete setup in under 15 minutes.