With the Schaller S-Locks presents Schaller the next generation of the famous Security Locks. Introduced in 1981, the guitar strap buckle system now features an extended 6mm screw axis for easy attachment to thick leather straps, while the new Lock-Wheel can be tightened and locked in place with a clamping screw. In addition, the specially turned 4mm thread of the strap pins ensures a secure hold in most common instruments.
Overview:
Schaller S-Locks Set consisting of two belt pins and belt buckles
My first set of Schaller strap locks came with a Fender Tele I bought maybe 30 years ago. They still work fine on that, it looks more likely that the strap will break before they do. I bought two sets for my two bass guitars and I like the redesigned locking system, which is compact and easy to install. It also means that if I want I can take just one guitar strap with me to gigs and just unclip each guitar, very efficient!
My go to strap locks - the new hex key integral screw for the strap button saves time fitting them. Also, the new screw on strap retainer is simpler to fit. Overall marked improvements on the previous generation of strap locks.
Probably one of the best you can buy. Easy to attach and gives peace of mind that will hold the guitar no matter what I do. Great service as arrived well before anticipated delivery date.
Schaller S-Locks (Black Chrome)
Schaller S-Locks (Nickel)
Ernie Ball Straplock Chrome 
Warwick S-Security Locks black