In the vast majority of situations, the Navigloo frame that comes in the standard kit is absolutely all that is needed for winter boat protection. The Frame Reinforcement Kit is an add-on to your Navigloo that offers extra strength. This kit includes an additional vertical post to strengthen the beam of the frame, along with two lateral struts for each side of the boat to support the tarp. While the reinforcement kit substantially strengthens the Navigloo system, it is important to follow all instructions as to the setup of your system and ensure that boat placement allows for snow to be shed from the tarp. So, if you get more snow than most, or if you can't get around to visit your boat from time to time over the winter, the Navigloo Frame Reinforcement Kit for boats offers a little extra peace of mind. Enjoy your winter!