They are the perfect size and I was hot to put one on my Suby engine where the A/C compressor was mounted. Very versatile connection wise too. They are good for up to 2.2 ltr. Only problem is getting a new one. Last time I checked only rebuilt ones were available. The real negative is that they have a problem with overheating. I have two friends who tried them. One just locked up and shucked the drive belt and the other barely will turn due to metal to metal contact. I'm not sure about what causes this but there is some suspicion that they are trying to turn them too fast.
I sure wish someone would get them straightened out. They are small and compact and would fit all kinds of small engines. They are about the size of two coffee cans laid side by side. Ford put this type of roots blower on their Lightning pick-up with excellent success..................Bruce