Just got an 12'' amsps tube for me 30'' MES new generation 3 smoker. OMG it works so good. smokes for 5 hrs to 6 hrs non stop.
put it on the left side under the water pan. it never stops smoking. its bad ass.
Have a look here: http://www.amazenproducts.com/SearchResults.asp?Cat=12
Amazen Smoke tubes and trays are a great invention for our hobby. Some of the trays will work with dust, others work with pellets, and the tubes (my favorite) work with pellets.
Like bqpig said, they smoke for a LONG time with a nice clean smoke, and are VERY versatile.