Norwegian farmers use "natural" MOEN Bells for their sheep, goats and cows.  The natural single-polished finish is darker and a little rough compared to the double-polished MOEN trophy and event collectible bells.  The photo with three bells shows both finishes. 

Measurements are from the bottom of the bell to the top of the metal handle.

3-1/2" high bell (Small) - sheep, goats, calves, BIG dogs
4-1/2" high bell (Large) - cows

Sizes also available in double polish only:
2-3/4" high bell (XSmall) - popular for hunting dogs, sheep, goats
4" high bell (Medium) - cows
5-1/8" high bell (XLarge) - cows
6-1/4" high bell (XXLarge) - for BIG Cows
11-1/2" high bell (MEGA) - for display (some elephants were interested, but the circus closed)

See photo below of very cool installation at Ruth Chris Steak House in Boston...the largest bells are the MEGA Bells.

Ribbons can be purchased separately.

MOEN Natural animal bells are also available with collars that have a patented attachment system to hold the bell tight into the collar.   A limited number of bells with collars are available.  Strap colors are red, blue, yellow, green, and white.