Replying to Proper all mountain ski size

Ok so we are looking at getting my dad a new pair of skis for his birthday but I am struggling over the issue of what size to get. He is 5'11'' and 210 pounds. Skis mostly groomers but occasionally dips into the trees or moguls. Decent skier, can make dynamic turns and go down pretty much any groomed run just fine. I was thinking a 181? Also I know the stiffness of the ski matters so I'll include that I am looking at a candide yard. (Gotta keep it cheap) help please