Materials：made of premium ABS plastic, strong and odorless. The minerals contained inside will not cause any harm to the human body so Easy to Use:Just put our mineral sticks directly into the spa filters or skimmers and let them do their work. Long Lasting：can last for up to four months and are virtually maintenance-free. So they are definitely the right choice for you to effectively maintain water quality at low cost. Easy to install: just drop the spa wand into an existing filter and let the hot tub wand work Widely Application:The minimum required filter length for the spa hot tub filter mineral rod parts is about 6.5 inches,and the minimum filter hole diameter is 1-1/4 inches.