The Purple Knot rubber medic bracelets are super simple and LATEX FREE! They come in one size fits most. Size of this medical alert rubber bracelet is determined by where you place the knot. We like to use a square knot which gives the bracelet a more finished look and is ultra secure. Simply ask someone to tie the knot while on your wrist or you may tie it yourself. Pull the knot tight and slip the bracelet on. Once the medical alert rubber bracelet is on and you are comfortable with the knots tightness you may cut the ends or leave them. This medic bracelet will be your custom fit! The Contempo ID offered with this bracelet is also interchangeable with most of the leather bracelets, all beaded bracelets, as well as the interchangeable medical bracelets.