Great stuff by Würth, perfectly suited for sealing engine cases, cylinder bases and gearbox covers. As soon as you tighten things up and the gasket is deprived of oxygen, it starts to dry and turns into a sealing layer which will easily withstand high pressure typical for these applications.
The cheaper version is the Würth silicone sealer, it remains elastic (like rubber), does not withstand pressure as high as the more expensive version, but is very durable when exposed to oil or fuel. In addition to that, it survives high temperatures rather well (up to 400° C); hence it may even be used for sealing exhaust downpipes.
Würth Silikon Special 250