A device for heating thermoplastic preforms, including a heating channel formed from a heating module and through which the regions of the preforms to be heated are guided by a conveyor device. Radiant heaters are arranged on a side wall of the heating channel. In the region of a side that lies opposite the radiant heaters and/or the base of the heating channel, reflector elements which act as counter or base reflectors are arranged. The reflector has a reflection layer and a carrier layer. The reflection layer includes a material with a silicon dioxide base and an IR reflection value greater than 90% in the range of 500 to 2500 nm. The carrier layer is a material with greater mechanical strength than the reflection layer and is used as a carrier for the reflection layer. Both layers have a similar coefficient of thermal expansion and are permanently interconnected.