Replacing broken spoke - size issue

RichR2 Posts: 131
edited October 2013 in Workshop
Broke a spoke on drive side rear of my Prolite Braccianos. Sourcing a new spoke from prolite or uk importer is impossible (gradually discovering how crap most bike companies after sales service is), so been trying to find alternative. Found some DT Swiss Aero Lite spokes but they only come in sizes 1mm shorter or longer than the quoted size on Prolites Tech page for Braccianos.

I've never done any wheel work and would like to know if that 1mm is critical and if not, whether its best to go 1mm longer or shorter. Thanks