The Fender Strap Blocks are a very reliable and hassle free strap lock system. With Strap Blocks, there's no need to remove or replace existing strap buttons on your guitar. All you need to do is simply slip them over the existing strap buttons and that's it. Your strap is securely locked in place.
Fender Strap Blocks work with most OEM strap buttons. They come in a pack of two pairs, one black and one red.
The main features of the Fender Strap Blocks include:
Simple to use
Work with most OEM strap buttons
Pack of 2 pairs, 1 black and 1 red
Manufacturer information
Fender Musical Instruments Corporation (FMIC) Cessna Circle 311 CA 92878 Corona USA contactemea@fender.com www.fender.com EU economic operator Fender (EDC) B.V. Transpolispark, Siriusdreef 17-27 2132 WT Hoofddorp Netherlands contactemea@fender.com www.fender.com
I am really happy with these strap blocks. They also work on a Les Paul guitar. They're a bit of a tight fit, but that's how you know they won't fall out.
Bottom line, they are a simple solution for a rather common problem.
Ordered with Richter strap and turns out it is so thick that there’s no need and space for these blocks. Too price for just a 4 piece’s of rubber shims
I much prefer these to the more expensive metal or plastic strap locks (which will affect the resonance of your guitar). These will keep your strap on.
D'Addario PWEEP202 End-Pins Elliptical chrome
D'Addario DGS15 Acoustic Quick-Release 
D'Addario PW-FLSB-04BK Flex Block Strap Blocks - Black