Spare 18 Watt UV tube for Blagdon cyclone filters.Blagdon Cyclone specific screw threaded PL-S lamps are compact UVC (germicidal) lamps used in Blagdon Cyclone Ultra Violet Clarifiers. The compact size of the lamp allows for a small system design and design flexibility. PL-S lamps offer constant UV output over their complete lifetime, for high system efficacy. Thanks to the single ended lamp base with intergrated ballast, lamp replacement is easy.