compact vs non-compact cassette and ring whazit?

At harris cyclery
Quality Bicycle Products Special Order Catalog
Search "cassette, I read-

Shimano
1mm spacer, to put a compact cassette on a non-compact body (FW8300)
$3.95

What is a compact cassette?
And what is a non-compact body?
Further,The ring pictured comes with the shimano cassette package? Or
is that included ring a different thickness?

I place the shimano cassette package's included ring on the installed
cassette becaws the ring comes with the package.

Currently, this means a 7 speed atb Cassette, ring spacer as pictured
installed between 1 and 2 cogs,then with 1mm ring spacer after 7cog(not
the one pictured, a plain round ring)-one filed off edge on a nylon
spacer-then a 34 tooth extra cog for 8 speeds on a deore lx hub.

Harris' catalog seems to infer that the pictured ring(s) are not
always called for but available for specific installations.

yesterday,the computer rejected the post as incomprehensible.
What's it all mean?

wrote:

At harris cyclery
Quality Bicycle Products Special Order Catalog
Search "cassette, I read-

Shimano
1mm spacer, to put a compact cassette on a non-compact body (FW8300)
$3.95

What is a compact cassette?
And what is a non-compact body?

See: http://sheldonbrown.com/k7.html#hyperdrivec

Sheldon "Answers" Brown
+----------------------------------------------------------+
| Men never do evil so completely and cheerfully as when |
| they do it from religious conviction. -- Blaise Pascal |
+----------------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

See: http://sheldonbrown.com/k7.html#hyperdrivec
and following data

good. i am completely,cheerfully, and principally relieved.
also, for the 7-8 atb conversion with a 1mm spacer, awl enlarge the
nylon spacer holes for the inboard cassette bump stops.

wrote:

...What is a compact cassette?...

It is a flat rectangular device that consists of a polymer case that
contains two hollow spindles that carry a reel of 1/8-inch magnetic tape
running at 1-7/8-ips. Commercially introduced by Philips in 1963 for
dictation recording devices, it became a highly popular (but medium
fidelity) media for music, both prerecorded and home recorded. Its
popularity has greatly declined with the introduction of optical and
other high density digital storage media.

--
Tom Sherman - Near Rock Island