These are even in the same league as Magpul P-MAGs.
I've only put about 100 rounds through each so I can't say that they're 100% reliable. They've worked in my 10" LMT and my 3gun rifle.
The mags are sold in pairs and come with a plastic tab that allows them to stay together. The followers do tip a little if you press only of the front of it unlike a P-MAG, HK mag or USGI mag with a Magpul follower. They're overpriced for what they are.
One neat thing about them is they're cut to work in an original AR18/180.