Generator Fuel Filter Change Question

[JBoyer]

Greetings all! This weekend, I attempted to change the oil fuel filter in my Onan 7500QD generator. Based on a post I had read, I purchased a set of flare nut wrenches - only to find they are useless on my rig, as the hoses are way to fat to slip them on. No problem. Decided to break out the box wrenches. I found the appropriate wrench for the filter side and the larger input side but I could not find a wrench, SAE or metric to fit the smaller diameter side that feeds the generator. I hope that makes sense. I have a Craftsman set of wrenches and thought I had a complete set, but obviously not. Everything I tried was either too small or too big. Does anyone know what sizes are actually used? I appreciate the help.