Here's a reprint of things I have posted on this site plus added material on electric stim things my husband and I use:
Read carefully and BE CAREFUL.
My husband and I have four electric stimulators and lots of insertable and surface/skin electrodes.
SexTek E312B---This has absolutely the most available power output of them all. If you are into pain, this is the one to get. It also has a tremendous number of stim cycles and it is the most customizable unit I know of on the market. You can even connect it to your computer for custom stim pulsing. It has a superb variety of stim cycles ranging from those that feel really smooth and gently tug at you to have an orgasm all the way to those that make you cum by feeling like the electrodes are grinding deeply into your body. This is also the most expensive--about $ 500 PLUS many different accessories. We got this about 6-7 years ago. It has by far the biggest battery and is a workhorse! You MUST read the entire manual with this stimulator. There is a lot you need to know. If you can't program a VCR, don't get this one!
Hotboxx----This one we found slightly more difficult to use and it has a longer learning curve than the simple Folsom units. It has a lot of cycles that can be used for pain, but not so many that give that smooth tugging buzz to the genitals. It was about $250+ when we got it s-7 years ago.
Folsom PSG 202----This one has some adjustability and gives a nice smooth tug on you urging you to haver an orgasm. I think it was about 150-200 8-10 years ago
Folsom PSG MAX----This has a more aggressive buzz and "grinding" sensation. This is really good as a butt plug energizer. It was about $200+ about 8-10 years ago
I hope this helps you make a decision. We haven't found the cheaper tens units to be as good for our purposes.
A few years ago, I bought my husband a bipolar urethral sound that we attach to our SexTek control box. The sound is designed so the inner part of the electrode goes in as far as the prostate and the outer part of the electrode completes the circuit in the portion of the urethra inside the glans. It is totally hands free and the while his penis is getting buzzed, I can insert another bipolar anal electrode to keep is bottom buzzing too. He also has one of the flexible conductive rubber catheter electrodes.
I also have a couple of vaginal electrodes for myself. One is shaped like a curved plate that is attached by elastic bands around the waist and it is a bipolar electrode that has an electric pad that sits on either side of the clit and labia. I also have one where the two sides of the bipolar electrode are on opposite sides of the "dildo" which kind of forces my vagina to contract on itself from side to side, and another one where there is one deep and one shallow ring electrode around the "dildo" which causes my vagina to contract lengthwise from inside-out. Both are a blast. Add a couple of warm wet fingers, and I'm in heaven.
We also have several different anal/rectal electrodes. There are bipolar ones about half the length of a hot-dog, unipolar ones also that size that are fully inserted, LARGE bipolar sausage shaped ones which may be fully inserted or left partially exposed, and butt plug electrodes in a variety of sizes. If you push the anal electrodes in very far, you can feel the buzz literally in your feet because the chorda equina (spinal cord below the level of the ribs) will get lots of stimulation.
For punishment devices, we have wire brush electrodes and needle electrodes, which are unipolar, as well as a Wartenberg pinwheel. I don't penetrate the skin with needle electrodes, but the fine point of the needle gives an extremely strong ZAP to the spot where it touches. The second electrode can go anywhere you like. There are also nipple electrodes, but we don't own any. I am firmly against any electrical devices that send energy across any part of the chest, even a bipolar electrode across a nipple. I don't need a cardiac event of any kind, thank you.
If you go to an S&M store in a big city, they may let you hold the various electrodes in your hand so you can get an idea of what the power control boxes feel like with the current flowing.
Some of the e-stim electrodes are sterilizable, vast majority are not. Things like butt plug electrodes do not have to be sterile to share, but they do need to be clean. Urethral catheter type electrodes must not be shared. Everyone must have their own.
Anyone with cardiac conduction problems, arrhythmias and the like, and anyone with neurologic problems like Parkinsons, Tardive Dyskinesia, Multiple Sclerosis (MS), or any other degenerative neurologic condition should probably find other ways to amuse themselves.
Play carefully boys and girls.