I bought the strap blocks because I already had had an accident with a guitar falling from a worn out strap. These blocks do a good job preventing that. Since they´re made of rubber, it does good not letting the leather holes of the strap slip along the metal of the guitar blots. If there is a defect, is on the durability. I have to take part of the fault since I do change straps quite a lot, whenever you remove the blockers and install them again it does some damage to them. So one of the ones I bought has a little crack already, but still doing its job as long as I leave it. So maybe, if you plan on using more than one guitar, better to let them alone once placed on the guitar. This way I think they can last pretty long. They are good for the price so you can get two for each guitar you have. Also a good thing about the material is that it fits into every type of standard guitar, whatsoever the thickness of the strap.