Features: Intelligent home 4-way relays expansion board, allows you to control highly voltages devices with low voltages. Up to 4 layer can be stackable, and you can use multiple stackable relays module to add many channel. The installation of the 4-channel module is simple and fast, just insert it directly onto board, then lock with screws and coppered column. Supporting multilingual development is great choice for intelligent home projects. Supports for Rpi4B/Rpi3B+/Rpi3B/Rpi2B/RpiA+/RpiB+. Specifications: Material: Plastic+Metal Product Feature: 4-channel relays Support AC3A 250V Support DC3A 30V Support relays status light prompt Support multilanguage programming Support address switching Support I2C protocol Easy installation Support for stackable Expand GPIO pin Compatibility with 24AWG-30AWG wire Independent of motherboards hardware (requires I2C support) Package Includes: 1x 4-way Relays Expansion Board 1x Instruction Manual 4x M 2.5x12+6 Coppered Column 4x M 2.5x6 Nut 4x M 2.5x6 Countersunk Head Screws note: Please allow 1-2cm errors due to manual measurement. Please allow for slight color differences due to different display resolution.