In 1981, Schaller developed and received the patent for a new type of strap closure with a unique design and great functionality. 37 years later, Schaller built on this with the S-Locks. Featuring an elegant Lock-Wheel, one-piece hardened steel strap buttons, an aesthetic design and perfect handling, they make it easy to be inseparable from your instrument.Simply screw in with an Allen key (size 3mm / 1/8 "), then the 4mm / 5/32" screw provides maximum grip on all instruments with existing standard size screws. The hardened steel and the double thickness of the strap knot guarantee maximum safety against breakage. The high-quality felt rings are there to protect the finish of your instrument. Due to the extended wire length you can hold straps up to 6 mm thick with the new strap locks. All S-Locks come in a new and attractive reusable crystal box containing a QR code to a video on how to install it.