I have seen a forestry flail take out trees as large as 8", but it is probably cheaper&faster to use a chainsaw. Comparing for forestry flails to a regular flail mower is like comparing a 22 rifle to the deck gun on a ship. I would way rather have a flail mower for my mowing choirs even a light duty one. I use a finish mower for most of my mowing, but it is hard on it. The stuff I have to use a rotary cutter for gets mowed once yearly, and doesn't have saplings bigger than 3/4 of an inch.