How small are you talking? Lab bitches are supposed to be between 21 1/2" -23 1/2" at the shoulders and between 55-70lbs. and males between 22 1/2"-24 1/2 and 60-75 lbs.
There are alot of breeders who these standards mean little of nothing. Although I believe that with the better nutrition available today the high end could be a bit higher (75 for mature females and 80 mature males)
Labs were always considered amedium dog but that seems to be going quicky by the wayside.