Atika've bought 319 008 Stirrer RW 1800 Twin in April 2013 on Amazon. So I have about 4m² concrete (also selbstgemischerter with gravel and cement) stirred, finished plaster and mortar. The device does what it is intended, with high performance. It is very strong and works so far in maintaining excellent quality. It has as I said not shown any problems with the material to be stirred above. For this price, I would take it again immediately.