The Multi-Well Holder is designed secure Heat-On inserts to the hotplate. Inserts are smaller than stand-alone blocks, and are available for small flasks and tubes/vials.
We recommend that the Multi-Well Holder is used when working with Heat-On inserts, because it is safer since the insert is secured to the hotplate (less chance of being knocked off), and there could be improved heat transfer from the hotplate compared to using the inserts alone. Furthermore, it has probe holes, while older inserts did not have them.
However, you may choose to use inserts on hotplates without the Multi-Well Holder.