Usually the window width plus 4–8″ on each side. Over one pole's length we join two with a splice.
Which base holds the crystal? — sold apart from it, in your finish
Rings close all the way round — the usual choice when each curtain stays on its own side of the middle brackets. C-rings are open at the back, so they slide past the middle brackets of a long rod (over 48″); choose them if your curtains draw across the whole width. With C-rings we switch the middle brackets to center bypass brackets.
A wand to draw each curtain by hand, usually one per panel.
To tie the curtains back, topped with your finials (end caps if you chose none).
How far from the walli
The projection is how far the holdback stands off the wall: the curtain tucks in behind it, so heavier or fuller curtains want more.