A kérdés egyértelmű.

Back in the day, watchmakers used natural genuine rubies to create these bearings, and more recently, they adopted the use of lab-created rubies (also known as synthetic rubies) or sapphires. The purpose of these jewels is to act as bearings to various components in the replica rolex watch catalogue specifically the parts that make contact and would normally wear down easily such as the escape lever and the impulse jewel.