On Fri, 7 Apr 2006 06:37:17 -0700, "Tom Nakashima"
wrote:

I could be wrong, but the yellow foam looks like a synthetic chamois type
material to keep the flies dry, or drier. Perhaps this is why 3M/SA calls
the yellow, the "dry fly box"?
Picture of the yellow foam:
http://www.burfish.com/page/BSC/PROD/3M/8-5709

I just bought two SA System X boxes yesterday. The yellow you speak
of is not the foam, but rather the space where the body of the fly
sits. The white (actually grey) section is the foam part that hold
the point of the hook.

Dave