I already had the Stihl RG-KM connected to a KM131R power head. I was curious about the Stens, so I bought one to compare. Short answer: they both work great, but with some tradeoffs. I was going to mount the Stens to a shaft to fit the same Kombi motor, but then I realised that it would fit my FS-311. That gives me a real harness and handlebar grips. Comfy! The 311 has a 28mm shaft, so no spacer sleeve required. It takes the largest spline adapter. Assembly is where I hit my biggest complaint of the Stens: Rather than use a longer cuff with 2 bolts, they opted for a single bolt cuff and a pointed set screw. This will cause permanent damage to the tube. My solution is to use the set screw to mark the tube, then drill a hole for it to pass through. Anti-rotation accomplished, and I can still change the head back to my wide swath poly-blade head when I want to motor through thick weeds. btw that big poly head is great, but I end up looking like I fell into a vat fo wheat grass smoothie. That aside, the Sten cuts great. It is very loud, and draws a fair amount of power. It has counter-rotating blades, but the bottom blade has the most exposed surface to the grass, so it will still lay down some material and miss cutting. A couple of swings cleans it up. Also the spinnig blads will spark if you bump into concrete (like the edge of a driveway). Now the Stihl RG-KM is very different. It oscillates, so nothing gets pushed out of the way. It is quieter, but there is a noticible vibration due to the oscillatory motion. It cuts so smoothly that I have sliced right through the ground under the grass without noticing. It is more expensive than the Stens, but it does come with a shaft. Power demand seems much lower, but I have no way to quantify that. It does spool up faster, and coasts longer. With the Stens, it stops dead as soon as I let off the throttle. The Stihl has a much beefier gearbox, but then there is a lot more going on in there. It is a bit heavier. So, the Stihl costs more, cuts better, uses less power, and comes with a shaft. It is configured for a Kombi engine, but I suspect that it could probably be fitted to a Stihl with a 1" shaft. The Stens is cheaper, and parts are available at a known cost. It is loud and soaks up a lot of power. btw I oil the blades of these units before and after I use them. I suspect that the Stens will quiet down as I use it more. The Stens does recommend sharpening the blades every 10 hours. That will be a pain. My approach will be a spare set of blades so that I can keep a set sharpened. And the Stihl? At the time that I purchesed it blade life and cost were a mystery. I will check with the dealer again. My recommendations: if you have a Kombi motor, go for the Stihl. If you want to adapt to a different system, the Stens is still a great option. Both are a dream to use. Caveat: I hate string trimmers. I use a Badger-head with poly blades for light stuff, and the largest Stihl poly head for big growth. That huge swath really speeds things up. It is faster than my clearing saw for everything but saplings. Both the Stihl and the Stens are recommended by their manufacturers as edgers.Are they nuts? I would only do that if somebody else is paying for the blades.
