I like the Ergo grip because they recently released a plug where I can keep the small allen wrenches for the optic/cheek riser.
Designed to plug the cavity on the bottom of our TDX-0 Tactical Deluxe Zero Angle Grips. Securely press fits into the bottom and helps prevent debris from lodging in the cavity of the grip. It also functions as a shock-absorbing pad to protect the grip when setting the rifle down on hard...
www.ergogrips.net
Big reason why I opted away from the MDT, MKM and other similarly modular grips.