DocRebuild is the only vendor to manufacture these part in house, on our own machines and tools.
We stock many different types of materials including Rubber, Sponge, Sheets, Rolls, Neoprene, Nitrile, Masticated plus Polyfoam, Cork, Felts, Corrugated. The following jpegs show some of the materials, tools and fixtures that support this enterprise. We even have tools to make our own Bin Boxes - 2" 4" 6" 8" 12" wide by 24" deep to store parts in the warehouse. Plus we even make some of our own shipping cartons.
Personally I believe the phony zip in Mechanicsburg VA doesn't produce anything from any of these material in house. One of their former employees wrote me that he would deliver a DocRebuild part to a totally different company in Richmond VA to get copies made. Probably that is why you often see Out of Stock notices accompanying a jpeg of "their" part.
The sheets below of closed cell sponge are approximately 4 ft by 8 ft.
The following 4 ft x 4 ft x 6+ ft tall racks have Gray, White and mostly Black
sponge rubber. We stock from 1/16" materials up to 2" thick.

These racks are also 4 ft x 4 ft x 6+ ft with different material thickness and
durometers - i.e. hardness, density. Using White chalk we print the thickness
of the material on the edge of the sheets. On the left rack below the top shelf
has 1 1/2 inch material increasing to 2 inch thick on the bottom shelf.
These following racks have various rolls of material: sponge, sponge with
PSA (Pressure Sensitive Adhesive), Neoprene, Fiber, Felt stocks.
More of these smaller racks have more rolls of material and the large boxes
containing sheets of Cork.
We call these Jumbo Rolls. These USA and Canadian Fiber material in rolls
are so large and heavy they have to be on wheels to move them around.
Just about every rack and fixture is on wheels. We plan on moving - there is
way too much crime in this city.
The following jpeg shows a 5 ft tall roll of Polyfoam.
Following is a 6+ Ft tall Jumbo Roll of A Urethane Foam on a Pallet Truck.
The White rolls are PSA that we apply to some parts, with some of the Knife
edge dies to the left.
More Knife edges dies for everything from AC to carb gaskets to Z and
everything in between.
More and more Knife edge dies.
This following rack has all the long Radiator Seals and Air Dam Knife Edge
dies. Ours fit and function perfectly because we got the GM Blueprints
directly from the former GM Director of GM Warehousing and Distribution.
Many Thanks again to Mr. Ken May (now retired).
Below is a 1972 454 Radiator to Hood Air Dam die - it is critical to keeping
your Big Block from overheating. It is exactly like GM - thanks to the GM
Blueprint. I had just cut a dozen or so 454 air dams from a sheet of sponge
and the remaining scrap sponge is sitting on the cutting pad.
What do you think zyp used for reference ? In the past 45+ years
I've never read anything where a GM blueprint was referenced by them.
We also have Proprietary Plastic injection Moldings, Solid and Tubular
Extrusions of many Hoses, Sheet Metal Stampings and even some
Fiberglass and Weatherstrips. And don't forget our innovative oOSOEZ
Wiring Schematics and all the clear accurate Instructions and Illustrations
included with our parts.