These pliers will form synclastic shapes like bracelets, hoop earrings and any other form that requires a concave surface. They come in three sizes 3/8", 1/2" and 3/4". The 3/8" will form a deep synclastic form with tight radiuses. The 1/2" does similar with less curve. Note: Anneal your metal.  

Synclastic Pliers 3/8" These pliers will form synclastic shapes like bracelets, hoop earrings and any other form that requires a concave surface. They are very easy to use. The 3/8 forms deep syclastic forms, 1/2 and 3/4 will do simlar forms but with less curve. Can be used with copper, silver, gold, brass, even stainless is possible. Aluminum works fine as well.

Synclastic Forming Pliers 3/4" These pliers will form synclastic shapes like bracelets, hoop earrings and any other form that requires a concave surface. They are very easy to use. Can be used with copper, silver, gold, brass, even stainless is possible. Aluminum works fine as well. Metal can be annealed or not. 

Double Cylinder Bracelet Bending Pliers 5/8" and 1".  Two different sized cylinders.

Double Cylinder Bracelet Making Pliers.  1 1/8" and 1 3/8" cylinders.

Double Cylinder Bracelet Bending Pliers 1 1/2 x 1 3/4