This is a 4/8 Cylinder Stirling engine from the German manefacturer Böhm Stirling technic. It has a sound like no other Stirling engine that i have. a deep roar that is very unlike the normal soundtrack of stirling engines. The sound is of course only the beginning of it. A highly desirable model that looks absolute serious, and in more ways then not, it also is. The movement underspeed is not possible to follow, but still it is a joy to run, the power of these compared to most Stirling models within reasonable size is quite astonishing. Very very powerful model for it's size of 2,5 kilogram weight.