@Apollo T.
It's a gray Wescott 9x10 wrinkle resistant.
Basically a large fleece sheet. Has a rod holder on top and I use small clamps to stretch the sides.
Works pretty good in keeping wrinkling and reflections to a minimum.
I drop a digital backdrop in post and use the overlay/soft light blending modes in PS.
Place digital drop layer, set blending mode.
Quick select the gray back first layer.
Blur to remove texture of fleece if necessary.
Invert selection and mask digital drop layer.
Fine tune and other adjustments.
The gray with overlay is forgiving and doesn't require much detailed mask work as long as the digital drops are pretty close in tonal value.
And if they aren't a brush here and there usually does the trick.
It's not close to a real painted backdrop and more work but it's fun, affordable and adds quite a lot of flexibility.