It's the most common and used type for correction.
It's one of transparent types and made of porcelain material. The ceramic's color doesn't change but it's more fragile than metal one. However, it doesn't mean that ceramic is less effective than metal and it's strong enough to endure whole treatment process. Most of all, it looks better with esthetic aspect.
This is another transparent type and material is plastic. It doesn't break but possibly its color could be discolored. However, this is also as effective as metal and color is fine within 1-2 year treatment period.