Flat head clear acrylic plastic standoff 13mm x 19mm  with a screw in head. 

Finish - Clear Acrylic

Dimensions
A - Diameter of head: 13mm
B - Depth of body: 19mm
C - Diameter hole to be drilled in sign for fixing: 8mm
D - Maximum panel thickness: 8mm

Available as single units, box of 100 or box of 300. 

Also available in other sizes:

clear acrylic standoff 13mm x 13mm (7237415)

clear acryclic standoff 19mm x 19mm (7237715)

clear acrylic standoff 19mm x 25mm (7237615)