PL-S and PL-L fluorescent lamp, which respectively stands for plug in lamp short version and plug in lamp long version respectively, are more commonly called as H shape or U shape bulb, depending on the glass envelope structure. They uses bent or connected glass tube to achieve a round lighting area. Due to the requirement of higher power lamp but compact sized bulb to replace traditional light bulb in smaller lighting fixture, plugin fluorescent lamp is invented for the purpose. They are widely used in home ceiling light, or outdoor wall mounting damp proof fixture. Similar to straight fluorescent tube, it uses halogen or tri-phosphor powder coated glass tube of diameter Ф13mm or Ф18mm, which power rating ranges from 5w, 7w, 9w, 11w, 13w, 18w, 24w. 26w and 55w. Plug in lamps usually use 2 pins or 4 pins base depending on sizes of the lamp, which could be G23 (2-pins), GX23 (2-pins), 2G7 (4-pins) or 2G11 (4-pins) base. H-shaped or U-shaped lamps mainly work with electronic ballast in the market. They use solid state mercury (amalgam), which make it more safe, stable and environmentally friendly product.