This is the e13 direct mount shiftring kit ethirteen have finally brought out a ramped and pinned 2236t and 2438t ring combo thats perfect for use with the ethirteen trs trsr and trs chain retention systems shiftrings allow for flawless dual ring chainguide setup the super strong long lasting 4mm exalite construction makes these chainrings exceptionally light and durable exalite is a special blend of 8 silicon iron copper manganese magnesium chromium zinc and aluminium for