Tear drop bezels are stainless steel 304. 

304 stainless steel is a high-quality corrosion- resistant metal. 

Rust-resistant: resists rust and corrosion with normal care, altogether it is not completely rust proof.

Durable: strong metal that holds up well to everyday wear.

Tarnish-resistant: generally maintains its appearance without easily tarnishing.

Low maintenance: easy to clean with mold soap and water.

Inner diameter is 10x25mm