As Paul says, the lugs are 20mm.

I agree with Paul too that they are a bit under-appreciated at the moment. The first gen case is the iconic one, that TAG-Heuer emulates now, but the 2nd generation was longer-lived and available in a large range of dials and case materials (if you include the Monza case with PVD and chrome versions):

6 different movements and 3 different case materials in those 8 watches :)

They wear quite a bit bigger than the first gen too, for anyone thinking those are just a bit too small (they're not, it's just smaller watches are out of fashion nowadays - better that than lugs hanging over the edge of someone's wrist in my opinion, that just looks ridiculous to me).