Have you ever drilled hinge-screw pilot holes, and then discovered that they were off-center when you went to install the screws? Pretty ugly wasn’t it - and hard to fix! These self centering drill bit guides prevent that. The nosepiece bevel centers itself in the hardware’s countersink, then applying pressure to the bit causes the nosepiece to retract, allowing the bit to drill a perfectly centered pilot hole. Drill bits are easily replaced by simply loosening a set screw, while the spring is replaced by unscrewing the hex drive shank from the knurled body. All drill guides come with standard 1/4" hex shanks for use in Quick Change chucks. Made in the USA.