Magpul has announced Gen M3 PMAGs with 10 and 20 round capacity. The 20 round PMAG is shipping now and the 10 round PMAG will be on sale in the first quarter of next year. Both have an MSRP of $13.95. The timing of this announcement is unfortunate, something Magpul acknowledged on their Facebook page, but these products would have to have been in development for some time and this is not a knee-jerk reaction to recent events.
The ten round magazine will be popular with hunters who hunt in areas that limit magazine capacity, shooters who live in jurisdictions that ban higher capacity magazines or bench-rest shooters who prefer not to have a magazine protruding from underneath their rifle.
The twenty round magazine protrudes less than the standard capacity 30 round magazines which makes shooting prone easier. The smaller size is also more convenient for compact PDW-style AR-15s.