I use TPS TSR Super Low rings on my 3-18x50 VX-6 and they work well. A friend of mine has the same scope and uses Seekins (Vortex PM) Low rings. The Seekins are a little more stout if you're concerned about heavy recoil. I like the slimmer TPS rings on my VX-6 because it allows room to mount a scope level next to the front ring. These scopes have very little room between the turrets and the objective bell. Other good quality rings that won't break the bank are Leupold Mark 4, Badger Ordnance, or Nightforce. With a 20 MOA rail you should be fine running low rings, whichever brand you choose.