【Length & Package】Length: 330 mm / 13.1 inches. Diameter: 25 mm. Sold in packs of 2 bulbs. 【Powerful Insect Control】The tube emits a wavelength of 365 Nm, which effectively attracts flies, mosquitoes, and other flying insects. 【Safe and Chemical-Free】Non-toxic, odorless, and chemical-free, and is 100% environmentally friendly and safe for babies and pets. The device is CE and RoHS certified. 【Applicable Model】Applies to most 20W electric fly swatters / mosquito killer lamps / insect killers. Note: Make sure the length and specifications of your previous lamp match ours. How to change bulbs 1. Turn off and unplug: Turn off the switch and unplug the insect killer. 2. Discharge: Use a screwdriver with an insulated handle to touch the high-voltage grid inside for 30 seconds to 1 minute. 3. Screen removed: Remove all screws from the screen and the outer grid on the side where the lamps are located. Squeeze both sides of the outer grid (left and right sides together). 4. Rotate and replace the bulbs: Rotate the bulbs until the base of the bulb meets the grooves in the lamp holders and remove them, replace them with the new ones, then turn a few turns to ensure that the new bulbs are in place and connect tightly to the lamp holders. Light photography and different displays may cause the color of the item in the picture to differ slightly from the real thing. The allowed measurement error is +/- 1-3 cm.