It depends....there are a few few different redboard iterations.

There's the original redboard but the lowest weight was 63g and had 63x5ct.

The 2nd gen was the ilima, and came in 60-70-80g.

The 3rd gen, M+ Plus, and M+ Limited Edition all come in the 50g description printed on the shaft.

Each gen shaft has "improved" materials and tweaks to bend profile.

Could you possibly specify a little more in detail what two exact shafts your referring to? That way I can post the correct webpages to the exact shafts you have questions about.

Thought I'd introduce myself.