i know that sintered is better than extruded but whats all the numbers about, is it the higher the number the faster it is, and how high can the number go and what does the number mean eg. sintered base 7700
Well I am no expert on bases, but I am quite adept at the google search...
Result #2 on "sintered base what do numbers mean" search...
"It is the type of sintered base used on the board - the higher numbers indicate higher density and pressure used to make the base material - the better base will have more "pores" and will hold the wax better resulting in a faster board"
Sounds like higher numbers = higher density. I am assuming that would also be more expensive, higher density = more materials used and higher amounts of force (energy) to create them.
The numbers indicate the actual molecular weight of the base itself. If the number is higher, that means the molecules themselves are larger. This means that there is more dead-space between these molecules creating a less dense base. Jmacphee9 is correct...a more dense base will not hold as much wax as it does have not enough space between molecules to absorb it.
More space between the molecule mean that more wax can be absorbed into the base. More wax causes more friction between your base and the snow creating more water....making for a better glide.
In a nutshell....a sintered base with a higher molecular weight will ultimately perform better when maintained properly....however they will not be cheap.