Info: Replacement Bulbs for Sperti Lamps; Sold in Pairs
The D/UV-F bulbs are custom made exclusively for the Vitamin D Lamp, model D/UV-F (which uses 4 of them). This video describes how to replace them (and shows which screws to remove to do so).
The model FR20T12/BL/HO Tanning bulbs are for use only with the Fiji Sun lamp. Fiji Sun bulbs last a very long time (approximately 1000 hours of use; tanning sessions should average approximately ten minutes of exposure time).