You need one of the Raspi cases (1st item below), and 1 intermediate stacking plate (2nd item below) for a second RPi. So, for 3 RPi: 1 case, 2 intermediate plates.
The bottom plate of the case goes at the bottom of the stack. The top plate of the case way at the top of the stack. The products come with all required parts (nuts, bolts, standoffs, etc.)
- Raspi case, stackable EUR 9.00