If you don't get any help here, I did a quick WEB search for 'cedar' and 'split' and found the following 2 sites that you can contact:
Meeker Cedar and Cedar+. The first site has an e-mail address that you can contact directly. The 2nd has (at least) a Webmaster e-mail address that you can write to for the proper person to contact for what you want to know. (Webmasters aren't known to respond to Customer questions on products.)
Anyway, if you don't get an answer at either of these 2 places, contact the place you bought them from or stop by a home where you see them being installed. My best to ya and hope this helps.