Those are good wires. They are relatively cheap but work just fine. They are very light and have a slightly different shape compared to other brands. Personally I really like the curved, concave shape, although that means less surface contact in some placements and may not be great in marginal placements.
The material used is quite soft, so they bite really well. However, because of the soft metal used, they worn a bit quicker compared to other brands such as BD and WC.
Because of their shape, they be placed in a horizontal crack nicely, with the abilities to "cam" when placed face down. There are only 7 sizes and the width to depth ratio is quite large. Personally I quite like how these are designed, but many of my friends prefer more traditional ones like BD stoppers and the WC rocks.
The plastic bit that ties the metal wire is quite weak. They start to come off after a while.
Overall, I think the Pro Nuts are good especially given the price. I also have a set of WC Rocks but 99% of the time, I carry a set of Pro Nuts.
My friends and I love these Camp stoppers. They are super high quality as BD's are, less costly, and we have had excellant luck in placements where even a traditional BD stopper won't work right or stay put. This is my 2nd set, and my partner (he's a avid BD fan - as I am as well) - liked them SO much HE even purchased a set as well. We love them! Gonna order myself a 2nd set as well of these!