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My takeaway lesson would be [...] to wear wool ‘boy short’ style underwear, free of any seams in the area of the saddle.

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Features I’ve found ideal have been a merino wool construction, a tight fit, and a longer-than-average inseam or leg length. For reference, most men’s boxer briefs have an inseam somewhere between six and eight inches, which I’ve found have a tendency to ride up while pedaling.