The Trojan 650686 filter system accepts the following UV lamp replacements:
The Trojan UV Max F4 - Whole House Ultraviolet System is a UV filter system that effectively reduces harmful bacteria, viruses, and Cryptosporidium and Giardia in your water. This whole house filter system utilizes a 110 watt UV lamp for premium water purification. The UV lamp of this ultraviolet water purification system needs to be replaced annually. With the Trojan UVMAX F4 system you will be able to purify water in variable water conditions.
Trojan UV Max F4 - Whole House Ultraviolet System specifications: