FlexATX is a PC motherboard form factor derived from ATX. The specification was released by Intel as an addendum to the Micro-ATX specification. It uses a subset of the motherboard mounting holes required for microATX and the same I/O plate system as ATX and microATX. FlexATX specifies that a motherboard be no larger than 9.0 x 7.5" (229 x 191 mm), and can have no more than 3 expansion slots.