I purchased this specifically to stamp rings with my ring mandrel laying on the sandbag. After stamping the first several letters I was loving it... so much easier than using a vice and having to tighten and loosen the clamp each time I want to turn the ring more to stamp. Then on my last letter, the heavy weight of the mandrel (because this size sandbag is too small to support the long mandrel) forced where I was stamping to raise and the letter I was stamping was misplaced... It was hard to hold the mandrel in place so that it wouldn't raise the top where I was stamping. Basically, I should have purchased the bigger sandbag for this purpose. My only regret. Can't criticize the product for that though as it was my mistake. :) My advice if wanting to use this to stamp rings, purchase the bigger size! Why didn't I think of that before. :) Seems to be a great product though and makes stamping rings easier/quicker!
On a side note: I did try it out to stamp regular blanks, using it as a base for my metal block and was pleasantly surprised at how stable it was and how well it held my metal block in place. I wasn't expecting that. I think I will be using it from now on as my rubber block I usually use is starting to get a bit too slippery after having used it a couple of years. Glad I tried it out! :)