The leather is a lot stiffer than the weighted leather stretchers offered here, but less stiff than some "strict" stretchers. The interior surface is lined with a softer leather, cushioning the skin.
They do take some breaking in at first since they come flat, not curled up, but a couple nights of wearing and they hold the round shape just fine.
For times when you can't or don't want to wear the weights they're fine. I wear one (2.5") at night and have no trouble sleeping with it on. I'm looking forward to moving up to 3" soon.
The weighted stretchers (I find the steel ones are best) are still a must since to really stretch things you need to pull on the interior connective tissues, not just the scrotum between penis and testicles.