I have posted quite a few ideas about armbinders so far and I confidentially claim, that armbinders are useful in self-bondage, but not all of them. Armbinders come in very different designs, materials and attachment methods. The most known armbinder is probably the one on the image below. I call these devices "armbinder" because this names them all correctly - they bind the arms.
This armbinder requires very flexible shoulders, which is a matter of training. It is said, that women can reach the right level more easily, but I suppose, that this depends on the amount of muscles rather than on sex. Of course, the average man is stronger than the average woman, and therefore less flexible. The arms are held together evenly over their length, which is much better than tieing together the arms above the elbow. This is what I call a monoglove, it fits like a glove.
Most armbinders from internet shops, ebay and the like are much wider at the upper end. I think, a perfect design would follow the outline of the arms from right under the armpits down to the wrists. An armbinder that is tighter around the upper arms than around the lower arms, will be uncomfortable, because most pressure is against a small area of the upper arms. I think, any armbinder that keeps the elbows at shoulder width should be fine for most people, this is an almost natural posture.
While the first armbinder is probably the ultimate sensation, wider ones are pretty cool too. I have an armbinder which is fairly straight, shoulder width at the upper side and it goes up to right underneath the armpits. In this armbinder, my arms are effectively tucked away and without undoing the shoulder straps, I can't get out. Unfortunately, most armbinders available on the internet are shorter. And even if perfectly tight around the forearms, I can slip out, because the elbows are not properly trapped.
Big trouble is the quality of many armbinders from the internet. Thin leather, brittle PU and similar material easily breaks. The attached straps come off because either the sewing is bad or the material at the attachment points is too weak, sometimes not even reinforced. Thin straps cut into the shoulders. Some straps are so short that they cannot be crossed over the chest, they will come off after some struggling.
So, what is a good model to buy?????
If you can, get the actual measurements from the seller. Wide armbinders should cover a good part of your upper arms to feel (and possibly even be) secure. For a start, I think a v-shaped or u-shaped design would be best, with the upper side shoulder-wide and the lower side wide enough to keep your hands side by side. U-shape with less than shoulder width cuts into the upper arms. If you are a man, look for armbinders that look a bit oversized on a woman (most armbinders are displayed on woman's arms). For solo-play, you don't need any straps around the arms (elbows, wrists etc.). Anyway, an armbinder is a design that should not need any such straps.
Some more info
Lacing is good if the binder is narrow, you can make it wider. But most armbinders from internet shops are very wide a
eady. But cutting the lace if everything else fails, is a way to escape. There are armbinders with a zipper instead of lacing. This could be nice if you have a plan be when the zipper refuses to operate. But don't try to push your arms together by closing the zipper, it will most probably fail or the zipper will break. You must be able to hold your arms in the right position.
Comfort
Look at the first image again - the very tight armbinder. You will see, that the upper arms are not compressed brutally, there is a straight line accross the upper end of the armbinder. Now look at the last of the attached images. You can see that the arms "bend" where they come out of the bag. There is no joint, the belt cuts into the arms and when you remove the armbinder from her, you will see a nasty red line.
There are a couple of threads about using armbinders here on the forum. One particularly interesting design is this model, which I am using without the extra straps. The shape of the "glove" is pretty good.
Some more images as attachment. Avoid the ones with neck-fastening, I think, they are especially dangerous in self-bondage. If you find an armbinder that looks like one on the first two images if you wear it, it should be fine for you. The third one loosk painful because of the strap above the elbows.