Jim
not extra thickSpend my working life in wellies and sea boot socks, bought these to replace worn out others. They are probably the thinnest seaboot socks i have ever bought in nearly 40 years of welly wearing. The sizes seam a mismatch, size 9-10.5 are actually 11's, but if they were tight they would be even thinner. I will continue to wear them and hope to be able to shrink and thicken in the washer / drier. Will by another type in future.