If you want to buy something that looks cool then get them. They are cheap so don't expect to be climbing 30 feet up a tree or trekking across a mountain. 1st off you don't use stuff like this for those types of actions anyways. If a ninja ever did use these to climb it was only a momentary pull because they help a little but they would have used good technique and not a hand claw to climb a wall or tree.
As for self-defense, the metal going all the way around the hand gives you a good area to fend of any sharp blades and if your good you can uses both hands and catch the blade with the spikes. Also the spikes may not be the sharpest but with a good scrape they will cut skin for sure and I'd wager that, that would be the main use of these devices.
Japanese Weapon
As for self-defense, the metal going all the way around the hand gives you a good area to fend of any sharp blades and if your good you can uses both hands and catch the blade with the spikes. Also the spikes may not be the sharpest but with a good scrape they will cut skin for sure and I'd wager that, that would be the main use of these devices.