To give you some reference I train to keep my hands in good shape for various activities, e.g. hand drumming, shooting handguns, and hammering. I don't have therapy/recovery issues and I can do reps with 200lb gripper easily. I own a range of heavy grippers plus a bunch of other grip training toys. I don't train for great strength - just for a level that is useful and protects my hands from injury.The product info is confusing. Here are the resistance levels from the Power Web website:1. Yellow2. Red/Orange Rubber/Latex3. Green4. Blue5. Black.The 7" is available only in 1 - 3.Different levels of stiffness are achieved by varying the thickness of the rubber mesh. Depending on how you do the exercise, you can vary the resistance of each level. For example a single handed grab is much easier than grabbing with both hands and increasing the tension on the web. Also, many exercises can be done near the rim or in the center which stretches more easily.I've bought a lot grip exercise widgets and most of them are fun but limited - some are junk. I was hesitant to shell out $20+ for the full size so I bought the 7" Orange and liked it so much I bought the 14" black.The 14" black:This thing is just fantastic. It's an entire hand training gym! It comes with a booklet showing 39 exercises which will give you ideas for 1000 more. I get bored easily and this allows for a lot of variety in my workouts. Its verstatility is amazing. You can work all motions of the hands and wrists very effectively. You can weave your fingers through the web, weave a bar or pencil through the web, push your fingers through and twist your wrist, lay your hand flat and flex or extend your wrist and much more. There are a number of specialized finger movements in hand drumming that require strength and flexibility in unusual positions. This is the only device that allows me to train for those strokes. I don't think this replaces a gripper for core strength but as a supplement it definitely would be effective. If I had to choose only one grip trainer this would be it.It looks very well made. The rubber looks like good quality and recovers from heavy stretching immediately with no signs of being stressed. Rubber can deteriorate, especially where I live, at high altitude, where there is a lot of ozone. Time will tell.Cons:This is larger than a dinner plate. Not something you can carry around like a gripper or squeeze ball.Yeah it smells of rubber. I like the smell - others hate it.Black is too stiff for the very weak movements like finger extension and some scissoring movements.The holes in the web are cut with rather sharp edges. If you have soft skin this might be uncomfortable on the stiffer grades. The red/orange is not a problem. Hey, man up and toughen your skin. :)My guess: If you can do 8+ reps with a 150lb gripper, Black or Blue would suit you. If you have average hand strength, red or green is probably a good choice. If you are doing therapy, I am not a physiotherapist, but I would guess you need yellow.The 7" Orange:I bought this to exercise various finger extension motions. While the possibilities are much more limited than the 14", it still offers a considerable variety. Also, the small frame means it's quite stiff when pulling the web away from an edge and lot easier if just compressing a section in the middle. So it offers a surprisingly wide range of resistance. It won't fit into a pocket but it's convenient for the car or to keep on your desk and it's easily carried in a pack or medium sized purse (no I don't have any sized purse - just sayin' :) ). It does not come with a manual.The Orange is just a leetle stiffer than I would like for extension motions but still very useful. It is also a bit lighter than I would like for closing motions. It's not much use for wrist work unless your wrists are pretty weak. For me this is a great all around item to take in my truck etc. I might get the lighter one just for the extensions. It's far superior to rubber bands.Considering that these cost about as much a as a good gripper, they are fantastic value in terms of the possibilities they offer. For anyone training his grip at any level, I would urge him/her to try this out. It's good enough to take a chance on the return postage if it doesn't suit you.Update: 14" Orange.I bought this for extension and scissoring motions because the black was too stiff for that. It's about perfect for me. Because of its size, the center of the web is much easier than on the 7" of the same color. I imagine that someone with an average grip, man or woman, would find this grade about right for finger contractions but too stiff for extension motions.The one serious disappointment is that for some reason, this model does not include the very useful booklet. Rather it comes with a short multilingual guide with far fewer exercises and insufficient explanation. I have this booklet from my purchase of the black model, but without it, the value of this device is greatly reduced. I certainly would not have realized all the possibilities and this review would not have been so effusive. I suggest contacting the mfr and asking for a copy.