Here's a copy or a recent post ...maybe it'll help It's hard to tell from looking at them. C and F's Look the same. G and K's look the same. The C-series machines were basically the first transverse-mounted engine jobs, and were a ground-up redisign.. F-series machines had the BICS system with electric brake and proportional auxillaries, and all revisions from the C-series are internal. G-series are again a ground-up redesign, easily distinguishable by the rounded corners on the cab and triangular headlights, with a more advanced (and more costly to maintain)electrical system. K-series(the latest) are again outwardly the same as G-series machines, with a redesigned electrical harness and a speed-controlled hydraulic cooling fan. The way I tell at a glance is by the decals, if they're still there.....=) C-model numbers top to bottom F-model numbers left to right, color coded green for medium frame and orange for large frame. G-all orange with rounded cab. K-the "Bobcat" Decal under the model number is rounded and sort of integrated with the model number-hard to explain but recognizeable. When ordering parts, Bobcat dosen't really care what series or year your machine is. They want the serial number and all parts and features are identified tracked by serial number alone.