Mini-STX


Mini-STX is a computer motherboard form factor that supports upgradable processors. The motherboard size is 147×140 mm, which is between Intel's NUC motherboards and Mini-ITX boards that are popular in small form-factor builds.
ASRock extended it by two inches to add an MXM slot creating Micro-STX.

Comparisons with NUC

When compared with NUC, the Mini-STX form factor:
When compared with Mini-ITX, the Mini-STX form factor: