Manufacturer spine sizing systems may be arbitrary (100, 200, 300, 400) and may or may not reflect the arrows' actual spine deflections (stiffness).  This system is different from one arrow manufacturer to another.  And some manufacturers list spine sizes in ascending order of stiffness - others in descending order.  So do not assume a 400 arrow in one brand is equal to a 400 arrow in another brand.  For example, a "Carbon Express Maxima 250" has an actual spine deflection of .404", not .250" as the sizing suggests.  So a Carbon Express 250 arrow has roughly the same spine deflection (stiffness) as an Easton 400.  To be safe, DO NOT assume an arrow's spine size is the arrow's actual deflection.  And DO NOT assume that what you know about one brand of arrow translates to another brand with regard to spine sizes.  See actual arrow specification data before selecting an appropriate spine stiffness for your bow.  If you need help, call our pro-shop at 877-410-7811 or email us for assistance.

I'm still confused.  Give me the full lesson from the top!