15mm inner dia, you can use it convenient for clasping 15mm diameter cable.A convenient cable-clip design noise suppressor , filter for RFI(Radio Frequency Interference), EMI(Electronmagnetic Inteference).In order to ensure the safety, reliability and purity of data transmission.EMI Ferrite Bead is adaptable to various kinds of digital products such as computer, digital video camera, charger and other digital product.