In reply to frqnt:
As has been said, pretty much everyone has their favorite screw, be it Grivel or BD something.
I happen to prefer BD Express'es.
The idea is to have one long one (ie. 22cm) for belays and makin' abalkov's. Your partner should also have one long one, as on multipitch climbs, you'll need to have two stands.
One or two stubbies (ie. 13cm) might be useful, especially early season.
My to-go screws are 16cm and it's what I use when the ice is good and compact. Maybe one 19cm screw would also be handy (shoddy ice, or to be used on the stands).
So, my suggestion is:
1 x 22cm
1 x 19cm
2 x 16cm
1 x 13cm
And your partner should have about the same. If you can get 6 screws... add another 16cm screw to the set.
This would be for cold climate ice falls. For summer alpine glaciers you'll prolly want longer screws (as the ice is not as good).