Angel Custom AP10 9mm Airsoft AEG M4 M16 to MP5 Adapter Conversion Kit
Magazine adapter MP5/UTR [Hades Airsoft] | TaiwanGun US & EU
ARES] Adaptor Set 9mm 45rds Magazine[For M4 AEG Series] – Asiaairsoft
Airsoft Evike.com - SMG mags or M4 mags? You don't need to choose with the Valken ASL! Comes with the SMG mag adapter so you can interchange = Best of both worlds!
King Arms PDW 9mm Airsoft Electric Rifle gun [MP5 Magazine Compatible, JASG Certified] M-LOK M4 [DE] - Airsoft Shop Japan