It’s an FSR for a ground support Tug! One of those airport things that pull the luggage trailer around. Seriously. Had to find a size that fit, that was it. Two row 1” tubes, 18”x18” aluminum w/auto trans cooler In lower tank. Now they actually make one for the A100’s but at the time it was look for whatever I could make fit. It did take some trial and error with the fans: missteps and redo’s but now it’s there.