We are always happy to share our knowledge about such a confusing theme. Firstly you need to dedicate your Series and Model of your iWatch. It is easy, just will look on the backside of your Apple Watch. So allow us to introduce our magic combinations: ● Apple Watch Series 1 - 38mm ● Apple Watch Series 2 - 38mm ● Apple Watch Series 3 - 38mm ● Apple Watch Series 4 - 40mm ● Apple Watch Series 5 - 40mm ● Apple Watch Series 6 - 40mm ● Apple Watch SE - 40mm ● Apple Watch Series 7 - 41mm All these Series and Models have the same size of silicone straps (On our store please press the button For model "38-40-41mm"). And the same thing for ● Apple Watch Series 1 - 42mm ● Apple Watch Series 2 - 42mm ● Apple Watch Series 3 - 42mm ● Apple Watch Series 4 - 44mm ● Apple Watch Series 5 - 44mm ● Apple Watch Series 6 - 44mm ● Apple Watch SE - 44mm ● Apple Watch Series 7 - 45mm (On our store please press the button For model "42-44-45mm"). We have many different types of straps so for these proposes we created a sizing guide, please ensure that your choice is brilliant for your Watch.