As the industry leader, Kwikset has provided trusted security for over 70 years and has become synonymous with security, peace of mind, style and innovation. The largest-selling deadbolt in America, the 600 series provides tough, effective protection at an affordable price. This single cylinder deadbolt can be locked or unlocked by a key on the outside or the turn piece on the inside. The crisp, clean appearance of the Satin Nickel finish adds to the overall look of the product and brings a modern feel.