I have heard good things about the Kindermann replacement cap and lid for stainless tanks, including that they accept and pour out liquid rapidly, so I decided to order one to try it out. But I was surprised when I read the instructions that accompanied the cap and lid set: "Cap and lid are made to fit tightly in order to prevent light leak." All my other PVC and stainless lids are light tight without the cap. Perhaps they mean in order to prevent "fluid" leaking? After all, the main point of the lid is that one can develop roll film with the lights on, with the cap snapping on and off as needed. What do you think? Thanks.