ASICMINER Blade Erupter Backplane Dimensions
The dimensions are as follows:

Hasher size: 233mm x 116mm with a 227mm x 100mm x 19mm heat sink attached to its back

Power module size: 192mm x 89mm

Ethernet controller size: 86mm x 40mm

Source:

https://bitcointalk.org/index.php?topic=204030.0