Great unit, adjustable speed is a must, especially if you are running larger bits. Coolant bottle works well, i use Slugger brand. I dont like the stress on the electrical connector on the top of the drill motor, i will do something about that but not big deal. I recommend paying a little more for the adjustable speed over the units without. I never ran it on full speed, didnt need to save the bits. And this unit''s top speed is slower than the non adjustable ones. So its a no brainer.