Frame size includes the body length and capacity of the lamb. You should try to avoid very small and very large frame sized lambs. Average to large frame score lambs should be selected to see economical gains. Lambs are typically slaughtered around 105-130 pounds, so something else to think about when deciding on a lamb is to make sure you can get them to their target weight in time for the fair. Lambs usually gain 0.5-0.75 pounds per day .
Ewes tend to be more expensive than wethers.
If you don't have any interest in breeding your own lambs in the future than choosing a wether would be a good choice. It is best to buy lambs in pairs because they tend to eat and grow better when they are together. When selecting a market lamb, you should consider the buying situation you are in. If you are going to an auction, generally the lambs are in racks . You should choose ones you are interested in and ask the producer to pull them out so you can make a complete evaluation of them.