The top can be made to most any size once the top or bar part of the pattern has been figured out. You then make the body of the halter with swirl motifs.

I used Bernat Baby Coordinates yarn (#3) , but any Baby #3 yarn will make a good substitution. Just make sure you get the exact gauge as stated in the pattern when you make a sample swatch. If your gauge is bigger than stated, go down one size in your hook. If your sample gauge is smaller than stated, go up one size in your hook.