Wetsuit gloves range in thickness from 2mm to 7mm depending on the style and brand. Most people stick to 2 or 3mm gloves but those who suffer from poor circulation will opt for a 5mm or 7mm. The various styles within the brands vary the linings, seams and thickness. All are glued and blind stitched with some adding taping or liquid seam to help resist water ingress.
Alder's glove sizings are quite generous such that many female customers end up getting a kids size, e.g. a glove size 7 is about a junior 2XL. C-skins sizing is much smaller so most people get adult sizes, ladies typically get their XXS(2XS) size.