First off, this leash is incredibly comfortable to hold. You wouldn't think so by looking at it but I have walked, run, skied and bushwhacked with it in every season and you hardly know it's there. Part of it is the soft rubber coating on the handle but it's mostly the moulded shape that snugs right into your palm.
Next, it is very strong. When my 65 lb male Samoyed goes after a squirrel, the half inch wide, spring loaded belt pays out until it reaches the end and whammo: full stop, no problem. I haven't cracked the case to see how the end of the belt attaches to the reel but it has stood up to this punishment nearly every day for several years now. Of course, this also speaks to how the spring-loaded, stainless steel D clip is fastened to the dog end of the belt: it's looped through, folded back and crimped with a plastic clamshell.
The leash has an elegant locking-mechanism that works reliably and intuitively by pushing a button with your thumb and then engaging a switch. This locks the belt at whatever length you want, and yep, it holds firm when charging dog meets end of leash. The belt is released just by pushing the switch again. Both setting and releasing the length are easy to do with one gloved hand.
When you run, walk or ski with your dog, the reel constantly pays out and retrieves slack (unless you've set the lock) so the belt rarely gets tangled the way other leashes can. This adjusts for both human arm swinging as well as for various dog movements. I sometimes clip the Flexi onto my belt, which frees up both hands for hiking or ski poles, or for carrying stuff.
Finally, it is almost completely silent. Impressive that in all seasons, with the belt getting wet, dirty and freezing, it has not developed the slightest squeak. — Tam Stewart