Extrusion sizes

Hi group,

there has been a lot of talk about extrusions, but no comparitive
data.

as I have gathered, the extrusions are either solid full diameter, or
open bottom. Depending of course on a solid bar as the rail or a
continous supported rail.

bearing/bushings are thin (for a better term) plastic liners,
(Ferlon/Teflon/Nylon or whatever)
or ball nuts, these being either fully enclosed with the balls only
touching hte shaft, or open carrage with the balls touching the shaft
and housing/extrusion.

my questions are what diameter is the shaft ?

The questions to the group are:

What shaft size are you looking for ?
ball slide or plastic ?

how many would you use in a year ?

In a typical application, it might be 4 for each table, or 12 for a
set-up. it might be 4 more for each to hold each rail end?

Dave