What's the difference between 1st generation and 2nd generation decking?

The main difference between 1st generation and 2nd geneartion is the latter one has an additional layer of a polymer sleeve that provides an impenetrable, wrap around protective layer.

1st generation decking also called non capped composite decking.  Wood plastic composite decking is made of wood powder, plastic and additives, and the Wood and plastic are carefully blended to create a solid and dense core.  While since 1st generation without the protective shield that the core is exposed under the sun, snow, stain,etc. So it's vulnerable to staining, fading, mould and mildew. 

2nd generation decking is co-extruded with a non-organic surface product to make strong, resilient board that keep their good looks and more natural. Beside, 2nd generation only need to simply wipe clean!