Is MEF or MEF2 baked into the .NET Framework?

I am trying to understand MEF and I am seeing references to MEF and MEF 2.

This site lists MEF2 as being much faster than MEF (4.0).

I need to understand what I am talking about when most people say MEF.

So which is in the .NET Framework 4.5? MEF or MEF2?

Well to make it even more confusing Microsoft released three versions of MEF using two only unique names: MEF and MEF2

• System.ComponentModel.Composition.* MEF in .NET 4 (typically called just MEF), no support for CompositionScopes, ExportFactories, etc
• System.ComponentModel.Composition.* MEF2 in .NET 4.5 (sometimes called MEF2 or MEF), support for composition scopes, ExportFactories
• System.Compostion.* from independent package Microsoft.Composition lightweight version of MEF typically called MEF2

The benchmark site refers to lightweight MEF2 System.Compostion.* from Microsoft.Composition package.