It might seam at first glance that both cameras are absolutely the same in size, but its not as it may seam. There is a slight difference.
- Measurements of Xiaomi YI :64 mm x 42 mm x 21 mm
- Measurements of SJ4000 :60 mm x 41 mm x 24.7 mm
As you can see, YI is lengthier and slightly higher, where as SJ4000 is few millimeters wider.