These new TTF sights are just off the line! They are an add-on feature, meaning if you already own a Catapult Carnage TTF slingshot, they can simply be mounted underneath the cone washers already on your catapult. Be sure to select the right size! Small, medium, and large refer to the size of your TTF slingshot, not the size of the sights. These sights are univeral, meaning they can be mounted for both right and left hand holds. Just choose the correct clip, and get to mounting!