Other important factors are ensuring the hardness and roughness of the shaft are correct. A shaft hardness of HRC 45 is recommended for a rubber sealing lip, with a roughness of Ra 0.4-0.8. A higher shaft hardness of HRC 60 and shaft roughness of Ra 0.1-0.4 is recommended for a PTFE lip.
Oil seal size
1) Common seal types and their features
What are bearing isolators?

Loosen the securing-clamp bolt at the base of the distributor, then carefully withdraw the distributor.
There are a wide variety of industrial applications and therefore there are a wide variety of oil seals to meet the specific application needs. By choosing the right oil seal you will have a better fit, improved stability, and enhanced reliability. Rubber tends to be one of the most commonly used oil seal materials. an oil seal manufacturer, explains how oil seals for and the importance of proper installation, “To provide effective sealing, radial shaft seals must be installed properly. An experienced installer with suitable tools, working in a clean environment, is recommended to provide proper installation. The shaft counterface surface and housing bore should meet the demands specified in the sections Shaft requirements and Housing bore requirements. To facilitate seal installation and to achieve initial lubrication, prior to installation, recommends wiping the shaft and seal with the lubricant that is going to be retained. While the outside diameter of metal-cased seals can be lightly lubricated to ease installation, the outside diameter of rubber covered seals should always be lubricated.