The choice of M20 foundation bolts is influenced by several factors. These include the weight and type of machinery, the expected dynamic loads, and the soil conditions at the site. The M20 bolt, due to its medium-large size, offers a good balance between strength and ease of installation The M20 bolt, due to its medium-large size, offers a good balance between strength and ease of installation
Leather Oil Seals - Leather Seals, also known as Type L Oil Seals, are most common in components that are subject to dirt and poor lubrication. Since they come pre-lubricated and are able to absorb fluids, leather oil seals are able to provide sealing properties in conditions that synthetic rubber is unable to.
Advantages of Silicone and Rubber Gaskets
What are Oil Seals and the different types?
Spark Plug Wire: Essential Component in the Ignition System

m20 valve cover gasket.
Please see the following for the types of sealing devices for bearings.
How to Select the Right Bearing (Part 7): Components surrounding the bearing

oil seal standard.
Several variables must be considered when selecting oil seals. The physical dimensions and materials will vary depending on the environment of use. In addition, oil seals must remain lightweight, compact, and exhibit high self-lubrication performance.
Special exceptions still apply within the Volkswagen group. With PTFE oil seals, an aluminium or plastic housing is used in many different engine series. The Top Dead Centre (TDC) signal is no longer measured at the flywheel, but directly using a sensor on the rear crankshaft flange and integrated sensor in the oil seal. Special procedures and tools must be used for the disassembly and assembly of these parts.