San Juan 21 or Mark I
This model was introduced in 1970 and produced until 1977.
It has a length overall of 20.50 ft (6.2 m), a waterline length of 17.50 ft (5.3 m), the design displacement was 1,250 lb (567 kg), but production displacement turned out to be 1,400 lb (635 kg).
It carries 400 lb (181 kg) of ballast.
The boat has a PHRF racing average handicap of 252 with a high of 246 and low of 258.

San Juan 21-2 or Mark II
This model was introduced in 1974 after about 1,000 of the Mark Is had been built.
The Mark II has a raised deck over top of the cabin and as smaller cockpit, with a commensurately larger cabin.
The Mark II was produced alongside the Mark I until Mark I production ended in 1977.
It has a length overall of 20.50 ft (6.2 m), a waterline length of 17.50 ft (5.3 m), displaces 1,250 lb (567 kg) and carries 400 lb (181 kg) of ballast.
The boat has a PHRF racing average handicap of 252 with a high of 267 and low of 240.
San Juan 21 or Mark I
This model was introduced in 1970 and produced until 1977. It has a length overall of 20.50 ft (6.2 m), a waterline length of 17.50 ft (5.3 m), the design displacement was 1,250 lb (567 kg), but production displacement turned out to be 1,400 lb (635 kg). It carries 400 lb (181 kg) of ballast. The boat has a PHRF racing average handicap of 252 with a high of 246 and low of 258.
San Juan 21-2 or Mark II
This model was introduced in 1974 after about 1,000 of the Mark Is had been built. The Mark II has a raised deck over top of the cabin and as smaller cockpit, with a commensurately larger cabin. The Mark II was produced alongside the Mark I until Mark I production ended in 1977. It has a length overall of 20.50 ft (6.2 m), a waterline length of 17.50 ft (5.3 m), displaces 1,250 lb (567 kg) and carries 400 lb (181 kg) of ballast. The boat has a PHRF racing average handicap of 252 with a high of 267 and low of 240.
San Juan 21