From Pathfinder Howl of the Wild, which isn't enabled.

Stoutheart Centaur

HERITAGE

You're a hardy centaur, firm of stance and strong of heart. You gain 10 Hit Points from your ancestry instead of 8 and gain a +1 circumstance bonus to Acrobatics checks to Balance and to your Reflex DC to avoid being tripped.

Pathfinder Howl of the WildORC