LOL, I am glad you "got it", I had a lot of guys with restoration shops not take that comment so well.
Here is a low down on fillers.....Duraglass would be found in the "reinforced polyester filler" catagory.
“Basics of bondo types”
"Regular" polyester body filler, and polyester "putty" is basically the same thing. They are both, you guessed it "Polyester" based. Polyester is what fiberglass is made of. The fillers have talc and some other components that give it "body", that is the basic difference between fiberglass resin and polyester body fillers.
The Putties have a finer ground talc than "regular" filler. They cost MUCH more, but are well worth it for skim coats and minor repairs. Being they are polyester they use a hardener and CURE like fiberglass.
The old "spot putties" DO NOT use a hardener and are simply lacquer primer . They are JUNK and should not be used.
Some examples of these products are as follows.
“Reinforced” polyester fillers:
These can be aluminum filled body filler for metal surfaces. I is very hard to sand and not good for the finish work (needs a skim coat of a “reg” filler or polyester putty) but will fill much more per coat reg filler and has more corrosion resistance.
A Fiberglass reinforced filler is similar.
Evercoat’s “Metal-2-Metal”, “Everglass”, “Kitty Hair”, “Tiger Hair”
3M’s 05815 Short stand filler, 05813 Long strand filler.
"Regular" polyester body fillers:
Evercoats RAGE or "Lite weight" and others.
3M's Lightweight body filler #058001
Evercoat's "Glaze coat","Metal glaze", "Easy sand" and others.
3M's "Flowable finishing putty"#05824 or "Piranha"#05821 .
"Spot putty" (junk, not recommended) Usually found in a toothpaste tube looking container.
Evercoat's "Ever-glaze" #403
3M's "Acryl-green" red or blue #05960,05964,05966
Dupont’s 2286S, PPG’s DFL17
I personally recommend Evercoat products.