FlexATX is a motherboard form factor derived from ATX. The specification was released in 1999 by Intel as an addendum to the microATX 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 × 7.5 in (229 × 191 mm), and can have no more than three expansion slots.