MOBRI RADAR REFLECTORS. This compact multi-angular radar reflector is accepted by professional mariners around the world for maximum radar visibility in all kinds of weather. No matter what your vessel looks like, make sure you can be seen with Mobri's unique, low windage, noiseless, chafe-free and light-weight reflector. The S-2 is designed for sailboats, and can be hoisted on a flag halyard or clamped to a shroud or backstay. The S-4, for sailboat mounting, is larger and provides a larger return. The S4 has a 4" diameter and is 23" long.