Sonoff’s Smart Stackable Power Meter (SPM) is a professional category, DIN-rail compatible, stackable relay with power meter and overload protection, with up to 20A per channel max. capacity. It can save consumption to a memory card (not an accessory).
This is SPM’s main unit, with Ethernet and LAN support, SPM stackable 4-channel relays are not part of the product, they are sold separately.