Summary: paper but if laminating it is easier just to put on drops of super glue on the face like shown above Any glue or even silicon that will stick to these surfaces should be alright Now remember that YOU WILL NOT NEED TO REMOVE THE NEEDLES to put on the new backgrounds removing them can damage the gauge and you have no way of knowing what position to put them back
Image Dimensions: 359 x 271
Image originally found here.