The smart watch bands and accessories sold in our store are sized based on the size of your Watch. When ordering a new watch band for, you will need to know its case size for the band to fit correctly. If you aren't sure what size and model your smart watch is, then you can find this information engraved on the top right side on the back of your watch. Once you’ve determined the size of your smart watch, simply pick the appropriate size when placing your order: Select 38mm/40mm/41mm if your watch is any of the following: 38mm Series 0, 1, 2, or 340mm Series 4, 5, 6, or SE, 41mm Series 7 or 8 Select 42mm/44mm/45mm/49mm if your watch is any of the following: 42mm Series 0, 1, 2, or 344mm Series 4, 5, 6, or SE45mm Series 7 or 8 49mm Ultra For determining your wrist size please see our Size Guide For any further questions on the sizing please email our support: support@selectbands.com