The diameter is about 18mm, which is the regular size suitable for most catalytic aromatherapy lamps, and please check the size before purchase control catalytic: the oil lamp wick can be lit with fire, or you can just put in oil bottles, and it has a good absorption effect, that can be applied with aromatherapy bottles and essential oils, bring fragrance to your room What can you receive: The sufficient quantity provides you a wide choice to meet your burner wick replacement needs in . Reliable and long-lasting: the catalytic core is made of various mixing materials of clay and fabric thread, manufactured by a good process to become a porous core, reliable and safe to apply, can service you for a long time Wide range of applications: these control catalytic burner lamp wick replacements can be combined with any ordinary catalytic fragrance lamps, and you can put on the table, desk, living room, bedroom, kitchen, bathroom, office, or other places, to purify and give you a good mood