A PCB preheater warms boards before removing parts for repair. This makes it easier and less traumatic to remove big parts like smd voltage regulators, TQFP and BGA chips. The hot plate can serve dual use as a preheater, but as the preheater manual explains this won’t work for PCBs with placement on both ends. This isn’t really a must have, but since seeing one in Bunnies workshop we’ve been on the lookout for one. List price was about 40 bucks before negotiation.