Most listings are marked one-size-fits-most or adult one-size. Some fleece-lined trapper hats include an adjustable head circumference (listed as 21.26–22.83 in / 54–58 cm) and a chin strap for a more customized fit.
Crown heights vary across listings (roughly 4 in up to about 10.24 in). Trapper-style hats often show a 0 in brim (no bill), while trucker-style caps shown alongside them commonly list a ~5 in bill.
Common warmth features include soft fleece linings, ear flaps, and insulated knit fabrics; some styles also add a chin strap to secure the hat in cold or windy conditions.
Many trapper hats use polyester knit fabrics for the exterior and a soft fleece lining for added warmth; some styles pair knit construction with full fleece interiors.