The slings I offer use a large, open, and unobstructed shooting loop to maximize the ease of looping up. I discovered that a majority of the time, slippage of the shooting loop is not an issue, given proper technique. The exception is when the front sling stud is mounted far forward on the rifle's fore-end. This reduces the angle of the sling to the arm, and when the sling is pulled taut it can slip.
To reduce the propensity of the sling to slip in this circumstance, I devised a simple sewn keeper that the shooter can slide down to close the loop over the bicep.
To put it simply, you don't really need it but it's nice to have, especially if you are big into shooting with a loop. One per sling works fine.
-IR treated 1.25" webbing.
-100% Made in the USA.
-Made for 1.25" webbing only.