The transponder holder 01 is used to protect a transponder. HDX transponders are mainly used in this product. This holder can be attached to the collar so that data from the cow can be obtained. The transponder holder is available in different colors. Transponders with a diameter up to 3 centimeters and a thickness up to 1 centimeter will fit in this product. If you are looking for a specific size for your transponder, please contact us! We will help you!