We were on the same pathHere are pics of the XL Jet Fins. These are the old ones, made in USA. Or maybe it was the 13 colonies back then. Note these are the "lightning" version with a different (better) rubber compound than the earlier ones without the lightning bolt.
Obviously the measurement is a little weird because of the shape and flexibility but the foot pocket opening is roughly 3" tall by 4.25" wide. Maybe a little wider. If anyone is going to measure their boot with calipers these fins could definitely accommodate a boot a little bigger than those dimensions accounting for flex.
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