|Where in force, the IALA System applies to all fixed and floating marks except lighthouses, sector lights, leading lights and leading marks, light-vessels and lanbys. The standard buoy shapes are cylindrical (can), conical, spherical, pillar and spar. Variations may occur; for example, light-floats. (See Buoy Shapes and Types for examples.) In the illustrations below, only the standard buoy shapes are used. In the case of fixed beacons (lit or unlit), only the shape of the topmark is of navigational significance.