Nope, The ARC 21 is the same as an ARC 21.

Designer
Roberts / Haberman

Specifications

LOA: 21' 6" (6.55 m)
LWL: 21 ' 3" (6.48 m)
Spar: 33' 0" (10.06 m)
Beam: 8 ' 6" (2.59 m)
Draft, Rudders only: 2 ' 5" (0.74 m)
Draft, Board down: 4 ' 3" (1.30 m)
Minimum Weight: 400 lbs. (181.44 kg)
Maximum Sail Area: 282 sq. ft. (26.20 m2)

Mine weighs 417