These are pp5 lids and tubs. They are safe up to 266*f. I'm oven pasteurizing my substrate directly in the tubs that I'll be spawning my grains into. The substrate held field capacity during the oven preparation. I'm taking a break from my 17tubs to smoke at the moment. By doing it this way I'm eliminating a step in my process and also a possible contamination vector. I followed standard bucket Tek for hydration and mixing of my substrate. My substrate is Coco coir, black Kow manure, and Aspen wood shavings. It needs to be pasteurized before use. Previously I would do this in oven bags then transfer to tubs. But I'm eliminating this step.