Magpul AR15 10 round magazine

These look like a 30 round magazine but only hold 10 rounds. Cost is $18 each. Anyone have experience with these?

I've used Magpuls in the past,
never had an issue,

but I don't own any , since I have a plethora of USGI 20's and 30's

- - - Updated - - -

I've used Magpuls in the past,
never had an issue,

but I don't own any , since I have a plethora of USGI 20's and 30's