Southdowns are a moderate sized breed of sheep. Although they are always white, they can have mousey brown faces and leg wool. They have medium weight, short wool with a width of about 25-30 microns. The wool is low-luster, so it dyes very well. It also has spiral crimp, so it is ideal for making items that experience heavy wear, like socks.

They are an closed face sheep and are naturally polled. Adult ewes are about 150-200 pounds and adult rams weigh around 225-250 pounds.

They are good mothers; their lambing rate is 140-160%. The lambs are early maturing and forage efficient. Southdowns have high quality carcasses