The Sentinel is one of the lightest mini HMS locking carabiners on the market, but more than that it is a really good multi-functional locking carbiner that works really well as a both as a small HMS and also, because of it's slightly offset shape, works as a great rigging/multi-purpose screwgate. This is because DMM has used a slightly offset design that increases strength and directs heavy loads into the spine, but uses gently curved top bar with a generous rope radius that allows it to work well with both single and double rope conrollers. The Sentinel works really well with almost any belay device and it fits snugly on most belay loops reducing the likelyhood of cross-loading. The Sentinel was redesigned in 2008 to feature a keylock nose so that it clips and unclips smoothly without snagging. It has a deep basket and good gate opening making it a fantastic and versatile rigging biner too that will take a couple of chunky clove hitches. All the usual DMM refinements are present - fully anodised, full strength barrels to resist push-in forces and conservative 3 sigma ratings.