Merged Pool is a "one pool wagering concept" which enhances the traditional pari-mutuel framework by allowing the turnover of different bet types to be merged into the same pool.
Quartet and First 4 will be merged to form the "Quartet & First 4 Merged Pool", with various enhancements:
Customers can still play Quartet and First 4 in the same way as they do today. The Merged Pool concept merely affects the mechanics of odds calculation.