Sturdy burr. I had to make doors for the puzzle box. I created three patterns for the door frames: a circle, a square, and an arched square. I made it out of 3/4 thick oak plywood and this piece handled each one with ease. I made templates for real doors. They consist of 3/4 red oak. I mounted my router on a table, taped the door templates to the top of the oak, then cut out the outside and moved the bottom bearing over the top template until I had a perfect match. It took a few passes but the end product was firm. Expensive but it's one of the best money I've spent. I had previously ordered a similar Yonico bit but it didn't work well for my needs. Highly recommended.