The MLG20.  The most common unit we sell here !   Absolutely perfect for drone spray rigs. We have sold dozens and dozens of them for that purpose isuzu 4 cylinder engine 4LE1 very die hard and reliable units. Very compact ver very quite 
Only 1 available  now 
Could be used for a house/building as well they do have automatic start features when being used in conjunction with a transfer switch 
The trailer tounge can be removed with 1 bolt to allow it to set on a trailer sideways 
1800 lbs 53 gallon fuel tank. 
Very fuel efficient 
840 hours