Ribs are made of food-grade, rust resistant stainless steel. They do not flex.
Rib measures approx. 6" tall by 2 3/4 " wide.
For an 18oz mug, use 1 1/4 lbs of clay. Throw a 5" tall, 3 3/4" wide cylinder. Also try Betsy XL as a goblet stem or bowl profile rib.