The I-20 is a modernized version of the M-20. It is a 20 ft (6.1 m) sloop rigged scow with a spinnaker. The boat was first built at Melges Boat Works, now Melges Performance Sailboats. The boat has two bilgeboards and two small rudders. After a couple years of experimentation, the class settled on its current rules in 2002. The new rules permitted a larger, asymmetrical spinnaker and a carbon fiber rig. It is currently made by Windward Boatworks. In 2005, Melges brought out a new Melges 17 to compete with the I-20.
 Class symbol | |
| Name | I-20 |
|---|---|
| Boat | |
| Crew | 2 |
| Hull | |
| Type | Monohull |
| Construction | Fibreglass |
| Hull weight | 595 lb (270 kg) |
| LOA | 20 ft (6.1 m) |
| Beam | 5 ft 8 in (1.73 m) |
| Sails | |
| Mainsail area | 114 sq ft (10.6 m2) |
| Jib/genoa area | 62 sq ft (5.8 m2) |
| Spinnaker area | 265 sq ft (24.6 m2) |