I have bought a few cylinders but never OEM. The biggest difference that I have found between a high and low quality cylinders is the rod and the seals. Oftentimes you get what you pay for when buying aftermarket. High quality rods are better steel, have better surface preparation, and may have multiple chrome platings. The idea is to keep rust away longer when not in use and weather exposed. However if the cylinder is stored in a retracted position when not in use, or use is frequent, then the rod is either automatically protected or is constantly being cleaned and lubed. I have purchased from my local Tractor Supply Co store, or online from various sites - do an internet search on "hydraulic cylinders". If you are looking for specific names, my quick list of online vendors includes Agri Supply (ASC), Agrimart, Quality Farm Supply, Surplus Center, Sloan Express. If you buy from brick-and-mortar, return or exchange is much easier. When it comes to specs, the key dimensions are: cylinder diameter, extended length (pin-to-pin), retracted length. Then there is the choice of connection ends - yoke, T-tube, etc. If only replacing one of a pair of cylinders, then make sure all of the specs match exactly. Cylinders that use a pin yoke that screws onto the cylinder rod can allow for a small amount of length adjustment. Hope this helps.