Here's the direct link to Forespar's excellent selection guide:Thanks for your advise, the purpose is to keep the jib open while sailing downwind.
Just remember if you have a headsail larger than 100% you will need a longer whisker pole than the standard one for you boat.For a Hunter 38 Whisker Pole By Boat Model (forespar.com)
Based on J dimension of 12.07 ft (base of the foretriangle measured along the deck from the headstay to the mast)
Forespar model: LC 1--18 #401106 Whisker Pole, Line Control LC 10-18 EL-UXP, Piston Outboard End, Complete Pole, 33' Boat Max. (forespar.com)
Fixed mast mount: part # 332025 Fixed Mast Flange (forespar.com)
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Great point!!. Suggest the OP confirm the whisker pole length matches your jib with Forespar or their dealer or non-Forespar whisker pole manufacturer........measure twice and buy once..........if you have a headsail larger than 100% you will need a longer whisker pole than the standard one for you boat.