A M16 Forestock model It can be a pen holder or putin a glass cup to be a drink cup (Internal dimensions 81mm diameter X 140mm high) also you can order another size for your cup the Picatinny Rail size are fit as a 1:1 airsoft gun so it should be fit as a real gun accessories Please rate if you like it And tell me your opinion (Also you can use English or Chinese) For inquiries, please find me at FACEBOOK: https://www.facebook.com/kwaileung.wong.9?fref=ts