The 901 and the 4075 do have interchangeable parts, BUT......they don't always play nice together. The 4075 batts are timed to burn hotter than the 901, so if u use a 901 atty w/ a 4075 batt, more of a chance of burned flavor. They're made by different companies. I must say the RN4075 is a fog machine.....and I do use both, but just be aware of the differences. 901 will be stamped w/ SLB on the ends. There are many threads on this forum that explain the differences, but these are the ones that I have experienced. Hope this helps.