Crown Mount Co-Linear Chimney Caps are the best option for venting a gas or pellet fireplace insert or stove in a masonry chimney. This unique chimney cap can accommodate the exhaust as well as the fresh air intake. No need to cut a hole in the side of the home, utilize the chimney for all your fresh air needs. The cap separates the exhaust and fresh air intake to ensure that the exhaust gas doesn't get pulled down the intake line.