This is a replacement charging handle for the GHK G5 GBBR. This model is a Large HK style with a solid center. It is oversized from the small versions and works well with gloves or large hands.
For a smaller version, check out the H&K Solid Small version, which is the same design but is closer to the stock charging handle's size.
It should swap straight across with minimal if any fitment or sanding, though occasionally a print will have slightly tighter dimensions and will need a little finishing work. Most common are the pin holes, which are difficult for the machines to make nice round shapes that small.
Part number: 10-01 Type-OK