Soto Muka Generator Unit. This is probably the most important part of the stove as it atomises the fuel before it is ignited (cool fact; Muka is Japanese for atmoiser.) This is why the Muka stove doesnt need to be primed like other, more traditional multi-fuel stoves. Soto testing has revealed that Muka stove performance will be reduced after continuous burning of 20 litres of fuel, so about 40 x 700ml bottles. That looks like a stupid bit of Maths but remember, the 700ml bottle holds 480ml of fuel. If flame output seems weak then replace the generator tube.