Mattress Helper Mini Under Mattress Support Extender- Fix Your Sagging Mattress No Sag Firmer Solution for Mattresses - Mini Extender DESIGNED *ONLY* AS AN ADD-ON for EXTRA LENGTH to regular Mattress Helper ONLY use for California King mattresses or as needed for EXTRA LENGTH - ONLY 18" INCHES LONG NOT TO BE USED WITHOUT regular MATTRESS HELPER Can be used for Couch support BUT MEASURE FIRST ONLY 18" INCHES LONG