OpenSprinkler 3.0 main controller is about 130mm x 70mm x 30mm (roughly 5.1in x 2.7in x 1.2in). Expander is 130mm x 80mm x 25mm. The cable is 30mm long and if you want you can use a custom made longer cable.
Regarding earlier questions about WiFi vs. Ethernet: here is an additional point: we do still sell version 2.3 upon request. We don’t regularly stock these any more, but if customer needs to buy we can still sell this version and there is generally a lead time of 1-2 weeks depending on how many orders of 2.3 there are.