kearing sandwich scale rulers are made of plastic,and all the reticles,lines are sandwich, laminated for durability.and all the lines are very thin but quite clear. 8501: 1/3 & 1/5 scale ruler. made of flexible & transparent plastic. sandwich line for durability. shanghai kearing stationery co,. ltd is the specialist and leading manufacturer in this field in china, and she is a high technology products manufacturer confirmed and awarded by shanghai science & technology committee.kearing can offer you every kind of scale rulers with top quality:1:3;1:4&1:5. all kearing curves have been selling well in both domestic markets and international markets for their top quality and best price. kearing curves sets have been exported to east-south asia,japan,america,europe,south africa etc. welcome international distributors and sales agencies to join us you can also visit our web site: www/kearing/com or :export/kearing/com for more information.