the modell 3 liner is a great coil -work and hit like a coil or can run like a sidewinder but very consistent and without to get hot or miss a beat. I have never to change any and can it adjust really fast and easy. The ultra rotary skinductor is more like a workhorse rotary but work smoother and have a consistent great hit -lining is very easy for a rotary. Very coil like - the ultra comes with 3 bars from soft ,hart and hart & heavy (3 to 4mm stroke) its funny to see this cheap machine have a better buildquality and functionality as some high end price rotarys. The hart r1 version lines better as a dragonfly x2 or stingray and have a better quality for near half the price