Seeedstudio Base Shield V2 / Board Compatible: The number of pinout is the same as that of Arduino UNO R3 So While using Arduino UNO with Base Shield v2, please turn the switch to 5v position; While using Seeeduino Arch with Base Shield v2, please turn the switch to 3.3v. Board Compatible: The number of pinout is the same as that of Arduino UNO R3. Attention: If using Base Shield v2 with Seeeduino V3, please solder the pads, P1 and P2. As an expansion board, Base Shield v2 has many Grove connectors, making it convenient for you to use Grove products together. And It is compatible with a series of Arduino products.