Dav
I use the same ring for both my shaft only and behind my balls, depending on how I feel like using it.
It’s this ring. I am very happy with it, it can be very easily adjusted to be very small or huge, that’s why you can use it both behind your balls or only for the shaft. Very easy to put on, very easy to get it off. Very easy to change the pressure. I’ve tried a few other types of rings which were either not so comfortable, or harder to put on and remove, or didn’t give enough pressure and therefor not enough expansion.
The only drawback about it is that it doesn’t look so sexy, and you are left with two pieces of rubber sticking out like two little rabbit ears! ;)
Oh, another drawback is that it’s too big to fit in the tube for pumping.
Anyhow - when you use it only for your shaft you get much bigger expansion in your shaft, it can be a difference of about 0.3". However I feel that putting it behind your balls is better for circulation so lately I usually use it like that.
It does keep a lot (not all) of your pumped up size after pumping, even a few hours later.
And, like avocet, I can’t be sure if it really has been beneficial for permanent gains (based on the cells repair in the pumped up state theory), but since it does makes sense and since it does feel good, and since the bulge in your pants does look good also, I keep doing it.