Generally the weight of inner pages is based on what meterials you select
The reference follow :
✔. Tomoe River Paper ( 52gsm/68gsm )
✔. Acid-Free Paper (90gsm/100gsm/120gsm)
✔. Stone Paper (120gsm/144gsm)
✔. Eco-Friendly paper(120gsm/100gsm/80gsm)
✔. water color Paper(300gsm/200gsm)