The Barton Windicator is available in 3 models: Model: Windicator W200L (Barton part# 84002). A wind direction Indicator for the Laser/ILCA lower mast. Can also be used on any mast with a 2.5" (63mm) 45-50mm diameter mast (round section). 100% accurate in 2 knots of wind. Weighs only 34 grams. Simple and effective clamp does away with the need for straps Model: Windicator W200OPTI (Barton part# 84002) Optimist Racing Model. Suitable for Optimist sailing dinghies. No holder. Vane arm length 200mm 100% accurate in 2 knots of wind Weighs only 22 grams 4.8mm shaft diameter. Fits into the mainsail luff sleeve at the top of the mast Model: Windicator 200S (Barton part# 84001)Racing Model. Suitable for sailboats 2-4 meters LOA Designed to clip onto Starling yacht masts. Also suitable for the Topper, Optimist or Blokart landsailers or any any sailboat with a 45-50mm diameter mast. 100% accurate in 2 knots of wind Weighs only 28 grams The Barton Marine Fact sheet on the Windicator range can her download HERE The following dinghy classes has been tested to confirm the Barton Windicator fits: W200S RS Terra Hartley Streaker Hartley H10 W200 L Byte CI - CII Fusion RS Aero 6 & 7 Hartley H12 RS100 RS Neo Seldon D+ Mast section D-Zero