costa del mar hammerhead backwater green blue mirror glass. what type of glass do they have the 400 glass lens?

Tech Specs:

Frame:

Metal 

Hinge Type:

Corrosion-resistant stainless steel 

Lens:

Glass 

Interchangeable Lens:

No 

Polarized:

Yes 

Face Size:

Medium, large 

Nose Pads:

Yes 

Arm Pads:

No 

Recommended Use:

Protecting your eyes, boating, fishing 

Manufacturer Warranty:

Lifetime 

Country of Origin:

China