Ensure you know whether the part order and received is a genuine HK part or an aftermarket part.
I was sent an aftermarket HK VP9 part which was supposed to have been an original HK small part. Were I not a certified HK VP9 Armorer I probably would have installed the part and been none the wiser until the weapon was returned to HK for some reason at which time HK would have been well within their right to void the warranty.