Size 90 - boat length 21 - 25 ft (90lb Force). Size 60 - boat length 15 - 19 ft (60lb Force). Size 40 - boat length 14 - 17 ft (40lb Force). Size 30 - boat length 12 - 15 ft (30lb Force). Size 80 - boat length 16 - 20 ft (80lb Force).
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