The FSR series was the only 2 piece crankcase where you could pull the front crankcase section and change bearings without having to pull the engine off the plane the VR ducted fan engines were two piece blocks also but the one you have a picture of is an OS Max 61 FSR I still have two of these with hundreds of hrs. on them over the last 20 years. You can't say that about too many other engines !!!!