hydrology ruler:7100: used in graphs-making for hydrologists. 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 sandwich rulers with top quality. 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.