Headliner!
A lot of you don't know a whole lot about one of my very favorite materials for cosplay; Headliner!
Headline is a sort of foam lined interfacing, it can be used to make muscle suits, line garments, fill out garments, make fake appendages... It is a fantastic and extremely undervalued material.
Headliner can most likely be found at your local fabric store, but it seems like most of the little cute old ladies at Joann's never have a clue what I'm asking for and usually sent me towards the foam and or Styrofoam aisles. Usually headliner can be found in the outdoor/ upholstery fabric section, and comes in production width(60") rolls. Sometimes if you're lucky, you can find it in the remnants bin.
Headliner comes in a variety of colors and thicknesses, and is ridiculously useful.
It can be put though a sewing machine, so go for it!
Happy Sewing,
Cheyenne