This is actually my second Fender Weighless strap so I was already familiar with the product before ordering from Thomann.
I first heard about these when I was looking for a strap that isn't that hard on my neck and shoulder. After digging and digging, I found these straps and they're total life savers.
First of all, I'd like to point out that this strap is mostly good for light instruments. Your average acoustic guitar and most of Fender's electric guitars are the best instruments with whom to use these straps. I would not recommend these for heavier instruments, such as most bass guitars out there. You can use these with them as well, but the strap begins feeling tight and uncomfortable after a while if the instrument is too heavy.
The point of these straps is that they're slightly elastic. The elasticity makes the strap feel softer on your shoulder than a regular strap—bearing in mind that a wide leather strap is another good option, especially for bass guitars. You would imagine that the elasticity makes the strap a bit more fragile, but I've had one of the red ones on my Fender Stratocaster for about a year now and it's still nice and bouncy.
Honestly, the only bad thing about these is the fact that the strap is rather uncomfortable with heavier instruments. If that's what you're looking for, I wouldn't recommend this, but for your Stratocaster, Telecaster, Mustang, SG etc. this is a good choice. The ends are very stiff and strong so I doubt that you'll see the guitar falling if you use one of these.
All in all, if you want to avoid muscle pain from playing guitar, this is a great choice. My back thanks me every day!
