Features: 1.Driver Chip:THB6128 with over current and over temp protection. 2.Made with 4 Layer RoHS PCB, strong and durable. 3.1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64 and 1/128 Microstepping. 4.Top mounted heat pad, this makes heat sinking a lot easier and does not rely on the already small PCB area for heat dissipation. 5.Easy to use DIR/Step interface. specification: 1. Driver Chip:THB6128 with over current and over temp protection. 2. Made with 4 Layer RoHS PCB, strong and durable. 3. 1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64 and 1/128 Microstepping. 4. Larger heat sink mounting area. 5. Easy to use DIR/Step interface. 6. Top mounted heat pad, this makes heat sinking a lot easier and does not rely on the already small PCB area for heat dissipation. 7. Output pins for Decay and external Vref. : Current Motor Supply : 2.2A max Motor Voltage: 35V max Size: 2*1.5*1cm/0.79*0.59*0.39in Colo: Blue Package List: 1 * SD6128 Stepper Motor Driver 1 * Heatsink 1 * Screwdriver Warm Tips: 1. Static sensitive - Handle with care, remove from packaging only when ready to mount. 2. Check mounting orientation before inserting. Drivers will be damaged when improperly inserted, can potentially damage host controller too. 3. Turn off power when connecting/disconnecting motors, do not insert driver when main board is powered. 4. Chip, heat pad and heat sink can get really hot, avoid touching while in operation. 5. Install heat sink with adhesive thermal pad, ensure that it does not come in contact with pins or any other conductive part of the board. Note: 1. The SureStepr SD6128 is a stepper driver board based on the THB6128 chip. It is simple to use and operate using an indexer (DIR/STEP) interface to move the stepper motors. 2. The SD6128 is a drop-in replacement for Pololu style footprint drivers including the SD8825, A4988, A4983 and Stepsticks. 3. One distinct feature of the SD6128 is that heat pad is located at the top of the chip. This makes heat sinking a lot easier and does not rely on the already small PCB area for heat dissipation.