I have modified and a made a few Stainless Steel devices and just discovered a really good way to test a new tube inner diameter without ordering the wrong size and spending all that money! 1. Start with the device you have (preferably Stainless steel) that seems a bit bigger inner diameter than optimal. Ideally, it's a device that has a good length for you. For example, it could be one of those inexpensive Chinese tube devices. A lot of these have a 1 3/8" ID tube. I'm finding the optimal fit to be a rather short, solid stainless tube, sized down to the minimum comfortable, and then a bit larger "Head" area with bars, like a typical Lori's device has. This also creates a sort of "bottleneck" that helps keep a device from never slipping down, as the head is mostly unconstricted and a tad bigger, while the shaft is a tad bit compressed throughout the tube portion, keeping it gently snug. 2. For $10, you can get this amazing stuff called instamorph at Amazon. It was quite easy to mold a thin layer of it uniformly inside my stainless cage's tube. You can shape it nice and smooth with your fingers. You heat the stuff to 140 degrees in hot water and them mold it into smooth plastic shapes. (One guy made an entire prototype chastity device with this stuff, including A ring, tube and PA fitting). InstaMorph - Moldable Plastic - 6 oz by InstaMorph Link: http://a.co/8bJFDK3 You could probably mold it just fine (with a bit more effort) in one of those devices where the tube is made from multiple stainless rings, and the advantage of those is that you can shorten or lengthen them a bit using a vice or other tools when it is off. 3. The advantage of this is that you can test any inner diameter, in any existing chastity device (that you think is a little too big). You can reheat it and reshape it as many times as you want, and try again. It turns clear and moldable at about 140 degrees F. And turns hard & white when it cools for a few minutes. You can wear it a couple days, overnight, testing those morning hard ons, etc. I use a little jojoba oil inside the tube to get it on and seated well and then it is very comfortable for me. 4. I wish I had done this earlier. It has helped me find my customized "tightest comfortable fit", which really makes chastity much more real and creates a perfect combination of comfort and security. Once you find it, you will strongly prefer it compared to those larger/ sloppy fit ball trap devices.