The SLR gas blocks have been the best for us in terms of ease of use and durability. We run these gas blocks on all of our competition rifles, and have yet to have a gas block fail in anyway.
 
Sentry Clamp On Version – Melonite QPQ Finish
15-position adjustability from 0 - .125" port opening
Gen-3
1.3oz
100% Gas seal allows full cut off and prevents gas from fouling metering screw
Complete disassembly is simple and take less than 10 seconds
Metering screw and screw bore design allows repeatability and reliability only SLR has been able to deliver
Single tool click to adjust gas metering
Melonite QPQ Finish 4140 Precision machined gas block
Melonite finish 4140 Nexturn Swiss precision metering screw
1095 Laser Cut Spring Steel leaf spring
Melonite finsh 4140 detent plunger
NO tiny springs to corrode, break or seize / NO tiny ball to seize or get lost
USES STANDARD GAS TUBE