Part #231 comes with one O-Ring seal that seals the adapter against the block where the stock disposable filter usually seals. All Block Adapters have machined O-Ring grooves to keep O-Rings in place so they don’t blow out or leak. All O-Rings are made of Viton® which is heat, chemical and fuel resistant. Block adapters have a machined hex to use a large wrench or adjustable wrench on to tighten the block adapter. Could also install a fitting into the block adapter then use a socket on the fitting to tighten the block adapter to the engine.