Just received the 6 liter unit a few days ago. So far, it’s fantastic! With a 25% dilution of CLR and reverse osmosis water, it’s cleaning the surface rust off my sockets in 20 minutes! It is IMPERATIVE to follow the instructions for having the unit FILLED with cleaning solution! It CLEARLY states that any less than 2/3 full and you will blow out the heater and transducers! I’m a former sonar technician from the Navy, so this makes PERFECT SENSE! I like this 6 liter unit so much that I just ordered the 30 liter unit for my larger cleaning needs. I intend on using these units a lot so if I have any problems, I will definitely change my review. So far, so good! Just FOLLOW the directions and you should have great results as well!