This is Two Rolls of 40"x6". This material is flexible, but rigid enough that it won't sag under the weight of the potting mix and water that is pressing down on it in the Bonsai container.
Excellent size of the drainage holes 2mm x 2 mm (approximately 5/64") and a thickness of 0.37 mm (approximately 5/32").
You should not use regular plastic or metal window screen wire like what is found at your big box hardware stores as the openings are much smaller which will cause some of your potting mix to clog up the holes and because the material is thin - it can sag under the weight of the soil and water in the container.
Video Tip: Holding Mesh in Place with DIY Clips: