There are a number of different lamp types and fittings, which are often specific to one type of heater, although there may be different types of lamp available for the same heater housing. Please select carefully; if in doubt, please ask.
Lamps are often available branded, eg 'Philips', or as a generic unbranded product. In our opinion, the price difference does not always justify the difference in cost. Burda lamps, however, are very expensive but standard lamps will not fit.