Russ Gilbert writes:
If you're talking standard computer store, you can't use those 5 1/4" disks.
I mean you can't use high density disks.  They must be double density to use
with the 1050.  Almost all double density 5 1/4" disks have a hub ring, high
density disks don't have the hub ring.

RHamiIton5 elaborates: (5/12/01)
The Atari 8 drives do not have write heads and circuitry which can handle the
type of oxide coating used on the high density floppy media; they cannot write
reliably to them. The hub ring has just become a sort of marker to distinguish
the high density from the standard double density diskettes.

Way back in your apple days of '79-'82, most disks were hubless and only the
really premium brands offered hubs to prevent slippage and out of round
problems; you could even buy little kits for adding you own hub rings.

When the home computer swell really hit around '83 and price wars began, hub
rings became common on good disks and eventually became standard down to
include most generic bargain diskettes.

The introduction of high density 5.25's required a different coercivity (=
magnetizability) to get more bits in a smaller space and suitable electronics
to do it. These disks were produced hubless; was it a differentiating label or
just unnecessary because of stronger mylar construction? Anyone?