The DuraVent Direct Vent Pro Co-Axial to Co-Linear Adapter Kit (Masonry Fireplace Adapter Kit) allows you to install a direct vent gas or propane fireplace inside a masonry fireplace. The kit comes with the adapter to connect to the appliance as well as the top plate connector, 4" x 6.625" High Wind Chimney Cap and two 3" x 35' aluminum chimney liners. The adapter will connect to the back or top of the appliance and transitions to two 3" flexible chimney liners. The two 3" liners will connect to the bottom of the top plate adapter and transition to a 4" x 6.45" direct vent end to allow the vertical rain cap to attach to the top plate. Check with the fireplace manufacturer's installation instructions to see if this kit is an approved installation for your particular fireplace unit.