Rotary shaft seal OAS-20X40X8-NBR

How to read the reference of an SPI seal at 123Bearing?
 Namely: references on spinnaker joints can not be used effectively to identify them. Indeed, each manufacturer uses his own referencing. The best way to identify a spinnaker joint is to measure the mounting: shaft diameter, housing diameter and joint thickness. 
These dimensions are regularly engraved on the joint.  Example: 
OAS-35X47X7-NBR 
Where 
 OAS = Shape of the spi seal 
35X47X7 = inside diameter X outside diameter X thickness 
NBR = material 
How to read the prefixes of an SPI seal?
 OAS = double lip with steel spring 
OA = single lip with steel spring 
ASP = double reinforced lip (up to 5bar pressure) 
BB = Single lip + single outer frame with steel spring 
BC = Double lip Single outer frame with steel spring 
DB = Single lip double outer frame with steel spring 
DC = Double lip Double outer frame with steel spring 
BD = Single lip, single metal outer frame, without spring 
CD = Single lip, without spring 
CK = Double lip, double steel spring

What is the difference between single and double lip?
A single lip seal will have a lip for the main seal of the seal, and the double lip seal will have in addition a secondary lip called "dust cover", used to prevent the outer elements from contaminating the oil or fat retained by the lip main. This secondary lip will also serve to preserve the integrity of the main lip.
Difference between NBR and FPM?
These are the 2 most used materials in mechanics. 
NBR is the most common and suitable for oils and hydrocarbons from -30 ° C to + 120 ° C. 
FPM is more resistant, especially at higher temperatures, since it withstands temperatures up to 200 ° C. It is perfectly suited to oils and hydrocarbons. Be careful, these 2 materials are not resistant to brake fluid. It will be necessary to move towards the EPDM.
What do you mean (the prefixes) OA, OAS, etc ...?
This is the shape of the spi seal. 
OA is the most common single lip seal, whose frame is embedded in the rubber. 
OAS is the most common double lip seal, whose reinforcement is embedded in the rubber. It is the most used in mechanics and fits for a large majority of montages.
Which seal to use for water / salt water?
The majority of spi seals will withstand water, especially at low temperatures. However, to ensure long-term resistance, the "FPMSS" material will always be supplied with a stainless steel spring, which will not rust in water.
What is the direction of rotation of the spi seal?
If this is not specified, spi seals do not have a direction of rotation (no oil flow streaks). So you can use them without worrying about the direction of rotation!
What is the mounting direction of a spi seal?
Although this may vary depending on the mounting, the side that has a spring is usually mounted liquid or viscous side (oil, grease, water ...). There is a variant of spi seal with a spring on each side, found under the type "CK". It will be advisable when the seal must be made between two liquids (oil and oil, water and oil, etc ...