Ulano Rubylith brand masking films are "light safe" knife cut films coated onto a polyester backing sheet. These films can be cut manually or on a plotter to produce masks for film contacting and plate making and film positives for photographic stencil production.
The backing sheet, or support, provides dimensional stability to the film. Although masking film coated to 300 gauge polyester is predominant, 500 gauge polyester is recommended when the application requires tight registration or the mask or positive is large format.
Rubylith Masking Film is a red masking film, suited for use with camera speed darkroom films as well as all screen printing stencils.

Ulano Rubylith Masking Film on 300-Gauge backing - Universal Tack 206-124-1 Roll RU3 Rubylith 40" x 150" $50.06 206-124-3 Roll RU3 Rubylith 40" x 300" $84.38 206-127-3 Roll RU3 Rubylith 52" x 300" $137.30 206-155-4 Roll D3R Rubylith 52" x 300" $122.60 206-500-1 Roll RU3 Rubylith 15" x 1800" $276.04 206-500-2 Roll RU3 Rubylith 30" x 1800" $471.98