Filling with a solution that is too hot can warp the plastic & damage the mechanisms. Containers are not "water tight", so pouring too hot can also cause leaking (until the formulation solidifies). Compatibility testing is always recommended. Set includes white oval twist-up tube gel snap on cap and snap on lid. 2 oz (57g) capacity Polypropylene. #5 Recyclable BPA Free (Product is not manufactured with BPA, BPS, DEHP, DBP, BBP, DINP, DIDP, DNOP, PFOA, PFOS, PVC, HIPS Mercury or Lead)