Here are the armor ratings for the armor table located on page-118 of the Orbit rulebook.
Just print this page, cut out the list and paste it into your book.

Soft Armor
Flak 2
Gelcor 4
Soft Armor: Silkalloy
Woven coats, pants and shirts, etc.)
Light 5
Medium 6
Heavy 7
Hard Armor: Battlesuit
(Composite metal sections mated to
Silkalloy clothing for added strength)
Light 8
Medium 9
Heavy 10
Hard Armor: Various makes
(Sealed armor suits)
K-7 "Kettle" 12
S'ssek 6
SmartWar Elite Trooper Armor 20
Void 8
Zha'kr 4