Just a heads up to any MDT Oryx chassis owners who want to swap the hex bolts that lock the adjustable cheek piece in place for tool free adjustments then the link below will save you a ton of money compared to the MDT offerings.
I've used these and they lock the cheek riser in place with zero slipping.
Total length: 20mm. Shaft is 10mm in length, including the thread, 5mm without thread.
www.ebay.co.uk