How do I choose between polymer-coated and anodised Heat-On? The Heat-On blocks, holders and inserts can be purchased either fluoropolymer coated or anodised. The polymer coating has been designed to give additional chemical resistance to the block. This is our most popular finish. Care should be taken not to damage the coating through abrasion/scratching, high temperatures, or chemical exposure. The anodised version is slightly lower cost. When working at high temperatures, we would advise selecting the anodised version of Heat-On, as then there is only the risk of discolouration, rather than damage to the coating.