The first electric stoves used heating elements made of high-resistance metal to produce heat. The stovetop (range) surface had one or more circular heating elements, insulated with compressed magnesia and sheathed in a spiral metal tube. Heating elements for the oven are of similar construction but an elongated loop to distribute heat. Elements were made as plug-in consumer-replaceable parts and could also be easily removed for cleaning. Temperature of cooking elements was regulated by adjusting a bimetal thermostat control switch, which switched power on and off to control the average heating effect of the elements.