The hardness of a stainless steel stem can vary depending on the specific grade of stainless steel used, as well as any heat treatment or other processing that the steel has undergone.

Stainless steel is typically measured on the Rockwell hardness scale, which ranges from A to C, with higher numbers indicating greater hardness. For example, 304 stainless steel typically has a Rockwell hardness of around 70, while 316 stainless steel may have a Rockwell hardness of 79 or higher.

However, it's important to note that there are many different grades of stainless steel, each with their own unique properties and hardness levels. The specific hardness of a stainless steel stem will depend on the particular grade and processing of the steel used.