Product description in 2007 mizuno introduced a sliding weight system called fast track to alter a drivers drawfade tendency mizuno has now evolved this breakthrough technology to also be able to customize spin rate and launch angle in the jpx 850 helping all swing speeds achieve maximum possible total yardage the piercing blue jpx 850 first seen on tour in april 2014 uses twin 8 gram weights which can be located on either the central sliding rail or two lateral slots with 10 unique setti