Anyone who has built, modified or maintained an AR-15-style rifle is familiar with the firearm’s family of small springs and detents. In an assembled firearm, many of the springs are under constant tension, and are therefore easily lost should they take flight during maintenance or disassembly. The Oops! Replacement Kit from DoubleStar is a good insurance policy against such frustrating, and inevitable, occurrences. The kit includes two each of the following: buffer detent spring, buffer detent, selector spring, selector detent, extractor spring with bumper pad, firing pin retaining pin; and four-each of: takedown detent spring, takedown detent. Price: $16. Contact: DoubleStar, Inc.; star15.com.