The Mayhew 66340 1/4-Inch Twist Socket, 8.25 mm-12 mm, 16-Piece, includes sizes 8.25mm-12.00mm in 0.25mm increments. Removes rounded or damaged fasteners with any head configuration (hex, round, square). One-quarter millimeter increments between sizes ensures coverage, regardless of fastener head condition or manufacturer"s tolerance. Manufactured from heat-treated alloy steel. No hammering required to install socket over fastener; twist socket tightens as more torque is applied. Additional applications include exhaust manifold nuts, studs, pipe nipples and corroded marine fasteners.. Each set comes packaged on sturdy, professional-grade locking socket rail. All product, including socket rails, made in USA. Comes with an unlimited lifetime warranty. Mayhew stands for quality, dependability, and confidence. When the caliber of the tools is just as important as the skills of the professionals employed, businesses trust Mayhew to get the job done. Since 1856, our punches, chisels, and pry bars have been the go-to tools for OEMs and professional mechanics throughout the country. And while our company has grown to meet the needs of the professional market, as well as those of the do-it-yourself automotive enthusiast, our focus has never changed - leveraging our strength to build your business.