C Prod. offers 20 rd straight mags that are "lanced" to 5 or 10 rounds, they also have ones that are "blocked", I know what blocked mags are but what the hell is "lanced" mag?
http://www.cproductsllc.com/shop/product_info.php?cPath=22_28&products_id=46
http://www.cproductsllc.com/shop/product_info.php?cPath=22_28&products_id=46