Stencils measure 2" x 3" and 1.8" x 4" and 2.75" x 4".  
Thickness: 15ml
 
JRV stencils are durable at 15mil thick. They are thicker than most other stencil lines. The most important way to get a clean stencil line is to use a good quality stencil brush and "offload" almost all of the paint on the brush. Stipple, or pounce up and down on the surface.