Nashbar's web site has a "Live Chat" link. Someone there should know the crank's specs.
Or contact Vuelta directly:
Vuelta USA
12350 Montague St. Unit L
Pacoima, CA 91331
USA
Bus: 818.686.3466 818.686.3466
Fax: 818.686.3468
Email:
sales@vueltausa.com
Their web site doesn't list that cranks but they certainly should know it's details.