The strap the I got isn't very long, about 6 feet but I'm not a very tall person (5' 0") so it works well for me. This strap is mainly for stretching the hamstrings on your legs, when you can't reach your toe you use the yoga strap. We don't use this very often in my class, it is usually used during the "reclining big-toe" asana, that's when you are lying down, your leg is up in the air, you grap your big toe and pull it towards your face. I can't do that, I don't believe half of my classmates could do that so I use my strap.
Most of my classmates use a stretch band rather than I yoga strap, the advantage to using a stretch band is that you could extend more, but I decided for the strap because it is more durable. Stretch bands could snap.
My favorite thing about this is that you can use it to tie around your yoga mat, and carry it around as a sling.
For anybody having trouble reaching their toes, and beginners who aren't flexible such as myself should buy a stretch band for yoga.