This is a fitting for garden hose. This is the end that would typically attach to an accessory or another hose. The hose barb is sized for a 1/2" hose and the threads are ¾-11.5NH (US and Canada standard). The hexagonal section is the same size as a 16mm nut (24mm between the flats).
You will need a gear clamp to attach it and it may require quite a bit of clamping pressure.
Printed in PETG, other materials may work.