You are not quite as big as other people, but that never slowed you down. You can't carry as much, but you are more agile. You get a +1 bonus to your Agility, but your carry weight is equal to 25 + (15 lbs. x Strength), instead of 25 + (25 lbs. x Strength). The extra stat point gained by this trait can be set on any other SPECIAL stat, like with Bruiser and Gifted.
Due to your small size, you have +1 Agility but your limbs are more easily crippled (25% extra limb damage).
J.E. Sawyer's Fallout RPG[]
You are smaller than average. It's hard for you to carry heavy loads, but it's easy to avoid the lumbering giants of the wasteland. -50 to carry weight, +2 to evade.
Lionheart[]
You are not as big as others of your race, but that never slowed you down. You can’t carry as much, but you are more agile. You get a +1 bonus to your Agility, but your carry weight is 50 pounds less than normal. Feralkins may not take this trait.[1]
Notes[]
When combined with power armor, Small Frame can have some odd effects. Your intrinsic carry weight will be calculated using the 15 lb/point stat, while the "bonus" carry weight from the armor's Strength boost will be calculated with the standard 25 lb/point. This means that if you take the opportunity to improve your intrinsic Strength, your carry weight will decrease by 10 lb.