1. Substance: 230g/m2-600 g/m2 2.Grade: B,F200,F300,F400,F500,F600,F700,F800,F1000, ... FB300,FB500 Our core board is mainly used to make high strength chemical fiber tubes, yarn bobbins, industrial paper tubes ... is as following:1. Substance: 230g/m2-600 g/m22.Grade: B,F200,F300,F400,F500,F600,F700,F800,F1000,FB300 ... dont hesitate to send me your inquiry at any time. high grade core board for paper core