I've been playing with this set since I received it a day ago. I think they are a good introduction to language and rhythm. I've never done much with a router before, so I didn't want to spend a lot of money on things I might accidentally mess up while learning. However, they appear to be vigorous and strong. The blades are sharp enough. The only downside I've found is that the single blade that forms the groove is thicker than the two blades that form the tongue. In use, they do not create a tight fit, but rather a loose fit of tongue and groove. There might be a way to bring the other piece closer with the two blades, I haven't checked yet, but either they need to be closer together or a blade thinner the hell makes a better connection.