Here is a plan to build a 4x5 sheet film developing tube that will maintain temperatures during processing for the sum of $15.00 This one I have proven to work beautiful. Before you use it make sure it is cleaned and dried throughly. The negatives come out beautiful. I have been processing T-Max 400 with Microdol-x 1:3 for 15 minutes then wash, stop, wash, fix for 5 min. I thought of selling mine but no way would I depart from mine. Going to go buy 3 more jugs. Wal- Mart sells these for $15.00 and they are not the coffee mugs. They are for soup etc. Try it you'll like it.