Sig has a line of Kavan props that appear to be a cross between an APC and a Master Airscrew in design and construction. They are listed in their site under nylon props (not very well listed in my opinion) and are both plain nylon and glass filled nylon construction. The plain nylon are yellow and the glass filled are black (the site doesnt specify this either).
Has anyone used any of these? The wide blade looks like it might make good thrust at lower rpm to me. Maybe a good 4 stroke prop?
They are made in Germany so I can imagine the quality will be excellent.
I have one but it will be a while before Ican test it.

got a web site to purchase these?

Many moons ago ( in the 70's ) I used a few of the yellow ones...6x4, 10x6...and I think I had an 11x6 as well.
I remember they seemed to be a lot like the Grish "Tornado" props. Good thrust, but loaded the engine a bit more than the Top Flite white nylon props I usually used.

Never tried the black ones...
Last time I got a Hobby-Lobby catalog (couple years ago ) they had the Kavan props listed.

They are on the SIG website listed under Nylon props, they have a yellow prop on the illustration but if you check the drop down menu you will find the glass filled ones and they are all black.

The props flex quite a bit, and should be cooked before use. When the nylon is dry it will be brittle. Cooking for 1/2 hour will restore full strength.
We have used them in RCcombat, and they performed very well with good speed, pull and spool-up. Their flexibility allows belly landings without damage.

Pe there are 2 different props under the Kavan listing. The yellow ones are plain nylon and very flexible, the glass filled ones are black and do not flex much. Otherwise the profile is identical.

I referred to the plain nylon ones. The GFR types should pull even harder.