The model FSLS is a 254 nm SW UV light specifically designed for fluorescent applications. FSLS stands for Filter Short wave Lamp Short wave. The TripleBright II is specifically designed for fluorescent mineral displays with special features such as its patented circuits (US patents 6, 479, 947 and 6, 838, 837) that allows the lamp (bulb) to be turned on and off millions and millions of times without affecting the life of that lamp. The cover is designed so that it can be opened once it is mounted inside the display case. Loosen the one captive bolt and the cover will swing open. The cover is held on by slip hinges so by sliding the cover lengthwise the pins come out of the hinges and the cover can be easily removed to replace the filters if necessary. Most other manufactures of UV display lights have sheet metal screws that have to be removed around the periphery of the cover and you cannot get to the back of the UV light when it is mounted in a display. The TripleBright II also has a fan to maintain the optimum lamp operating temperature for maximum UV output.