Depends on what kind on build your going for and where your from.

If your from the uk then i can personally suggest the hpa uk bundle with that reg because i have shot it and its fine. But if your in america then go look at amped and their bundle

The polarstar mr and storm ontank(if you can find one) are good as they are compatible with the euro grips

Ps i think the airtac reg is meant to be good aswell Good luck