#3 wires, 5.5mm diameter wire to fit up to a maximum book thickness of 3.5mm, around 30 sheets of 80gsm paper
#4 wires, 6.9mm diameter wire to fit up to a maximum book thickness of 4.8mm, around 40 sheets of 80gsm paper
#5 wires, 8.0mm diameter wire to fit up to a maximum book thickness of 6.4mm, around 60 sheets of 80gsm paper
#6 wires, 9.5mm diameter wire to fit up to a maximum book thickness of 7.9mm, around 75 sheets of 80gsm paper
#7 wires, 11mm diameter wire to fit up to a maximum book thickness of 9.5mm, around 90 sheets of 80gsm paper
#8 wires, 12.7mm diameter wire to fit up to a maximum book thickness of 11.1mm, around 105 sheets of 80gsm paper
#9 wires, 14.3mm diameter wire to fit up to a maximum book thickness of 12.7mm, around 120 sheets of 80gsm paper
Please note that the number of sheets is an approximation as different papers vary in how they bulk up. Also, you will need a 3:1 Wire Binding appliance to successfully use these wires.