I have four 150 foot rows of smaller trees that I try to keep weeded. The weeds grow very think and many get to 3" around at the base. I started using the new Stihl premium trimmer line on the FS90 and I was getting covered in weeds and it was fairly slow and taking a lot of power to keep the line up to speed. No issue with line wear, I just needed more power.
Back to the barn and I grabbed the FS130 with the brush blade. Sort of a circular saw type blade and I went back out. This blade is great for cutting down very large based weeds but it lacks the "gap" to deal with very thick weeds. So I took a trip to Ace Hardware on a hunch to test out a Brush Knife I seen there.
I was hesitant at first, but this is the best bolt on I have ever put on a trimmer. I had the "gap" to get into any thick nasty weed mess and cut everything like butter. I took out two 3" cedars on accident as I did not see them in the weed mess. I was cutting through alfalfa and many other weeds with 2-3" bases like nothing. This was like having line on the trimmer, but the line being a razor blade. My circular saw type blade would have needed to be swiped back and forth 5 times to go through what this brush blade would go through in one swipe.
I did not have a power issue at all and found it ran great at about 1/3 throttle. This was an absolute joy to use. I hit dirt clumps and rocks many times with little to no damage to the blade. It reminds me of the rotary cutter blade as its not sharp nor does it have much of an edge, but it cuts everything,
You do need to have pants, long sleeve shirt, some sort of face guard and safety glasses as it throws some serious trash. But you will be smiling as it cuts everything in sight.
Below are pics of it on my trimmer without the guard so you can see the blade and also a picture of what I used to use. Another great product from Stihl!