This cup does not move, there are three strings to hold it in (and may take some getting used to). There is plenty of room to situate yourself and secure the cup in. If anyone strikes your groin they will know it! Unlike plastic cups that flex the steel cup will punish anyone who strikes it with a nice bruise!
If you tie it tight it works fine for grappling, but it definitely made for striking. Works well for MMA and like I said, you won't feel it but your opponent will. For serious fighters.
A great cup, larger than more plastic cups and made of steel. When you do get hit, the steel takes more of the impact.
Personally, I took the straps off and stuffed it into a regular jock strap, works great, doesn't move and I don't feel like I'm wearing a thong.
The Windy Cup is clearly the best choice. The Steel cup offers the best stability and protection. Once it's tied on it does not move or slip out of position like traditional athletic support/cup. The padded edges prevent it from pinching the skin. Even in the vent of an accidental strike to the cup area, you have to be more concerned with your training partners safety afterward.
Ever since reading about an accident where someone got kicked in the groin while wearing a plastic cup, and having it split, bend inwards and tear the foreskin off I've refused to wear any cup other than a steel. It just doesn't make sense.
I've tried wearing it several ways, with the strings it comes with in a couple different configurations as well as inside a Shock Doctor compression short. Definitely the best option is with the strings. It stays in place that way, while it can move in the compression short. The down side with the strings is where the knot is becomes very raw if you're doing ground work on your back. This isn't really a huge problem, as you should be able to protect your balls without a cup if you're just doing grappling, and if you're including hard striking the discomfort is nothing compared to having the cup split and rip your boys appart (I've not had this happen, but it's one of those things you don't need to experience to know it'll hurt).
The leather padding around it is great for comfort, and if you're wearing underwear such as Obviously or Sakks that keep your jewels centred and in front, it's wide enough that there's almost no chance one of your balls will slip out to the side and get squished between the cup and your thigh as is the case with the more conventional cups.
Given that a single steel shell is very reliable, these are very cheap, and the down sides are merely inconveniences and not measurable compared to the clear benefits - I'd need some serious convincing to move to anything else. I've taken hard knees to the groin in the clinch while wearing it and while it still did hurt a bit, I was able to finish out the training session without having to take a break to recover. The fact that it is very inexpensive is just a bonus.