双线圈
双线圈优点：能平翻至180度，便于翻阅；能够360度翻揭；跨页图文能够对称拼合。
齿距 pitch | 型号 size | 内直经 coil diameter | 建议最大装订厚度recommended maximum book thickness |
3:1 | 1/4” | 6.4mm | 4.8mm |
5/16” | 7.9mm | 6.4mm | |
3/8” | 9.5mm | 7.9mm | |
7/16” | 11.1mm | 9.5mm | |
1/2” | 12.7mm | 11.1mm | |
9/16” | 14.3mm | 12.7mm | |
2:1 | 5/8” | 16.0mm | 14.3mm |
3/4” | 19.0mm | 17.5mm | |
7/8” | 22.0mm | 20.6mm | |
1” | 25.4mm | 23.8mm |
