I use quality. 2mm mylar/plastic type stencil sheets. They are thin and flexible but not as thin as paper. They are NOT the cheap flimsy paper thin transparency sheets I've seen used before. These are the best quality material sheets I've been able to find so this is all I use.
Disney Alphabet Letters Numbers 1.2 Font 11 x 8.5 Custom Stencil FREE SHIP
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Disney Alphabet Letters 1.2 Font 11 x 8.5 Custom Stencil FAST FREE SHIPPING
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DISNEY ALPHABET LETTERS Numbers 1.2 Font 11 x 8.5 Custom