Review: Pint-Sized FN 503 After 1,000 Rounds :: Guns.com
Addressing the elephant in the room, it compares well to the Glock 43. In fact, it is just slightly shorter. They share the same standard magazine capacity, but the FN-made gun comes with steel rather than plastic sights. Glock's single-stack 9mm runs 6.26 inches overall due to a 3.41-inch barrel. However, the G43 is a hair shorter than the FN 503, which stands 4.25 inches tall with a flush-fit 6-shot mag inserted. FN 503's included extended 8-shot mag with a grip sleeve adds about an inch to the height. It is an apples-to-apples comparison to the G43 with aftermarket tactical mag...
Source: guns.com