I have a question about something I just noticed today regarding SS tanks. First, let me state that I've been a plastic reel user all of my photographic life, so my discovery today was a surprise. And I don't want to start a plastic vs. stainless discussion. I'm just trying to clarify facts in my own mind. Over the years I've collected a small handful of SS reels and a couple of tanks as tag-alongs in auctions I've won while looking for other things. I just have them on a shelf basically doing nothing. A friend asked about them, so I was demonstrating how they were used. My meager stainless collection consists of a no-name 35mm single reel tank with a defective light trap, a Kalt 4 reel tank with reels and a little doo-hicky to lift the reels out of the tanks when you're done, and single Nikor 120 tank with a 120 reel. So I demonstrated how one reel went into the 135 single tank, how the 120 reel went into the 120 tank, and how the 4 reels went into the 4 reel tank. Then I said you could put two 35mm reels into the 120 tank like a Paterson. So I stuck two 135 reels into the 120 tank. They did fit, but to my surprise they completely fill the tank. Right up to the top next to the lid. There is practically no air space in the tank if you pour in enough chemicals to cover the reels. And absolutely no overhead room. So my question, are stainless tanks designed for 2 35mm reels slightly taller than stainless tanks designed for a single 120 reel? If not do you run the risk of the top edge being uncovered if you're not careful when developing two reels? Or is this a Nikor anomaly, and other brands of stainless tanks the 120 single and 2x135 are the same size? I know the Kalt 4 reel tank has plenty of overhead room just because the metal lifting rod pokes up a few mm. I would think that a 2 reel 35mm tank would need some extra room so you can agitate. But being a plastic kind of guy, I assumed that the 2x135=1x120 and they were really "the same tank" between them. Any clarification from a dedicated stainless tank user?