.
It was 8.75 for a while, but I think 8.5 is about it right now by a hair. Even 8.38 is pretty close, but some of the 8.38s are pretty much 8.5 anyway, at least that's how I ride them and sell them to people who want a little bit lighter 8.5 board, almost all DLX wood too, but a few other BBS brands. Some 8.25 loyalists as well still keeping with what was their most common size for a long time, but I think I move twice as many 8.5 / 8.38 boards as anything else.
Wheel is maybe 54 mm, but even the 52 mm wheels are making a comeback again after people find that most other wheels are too big again now, pretty much only Spitfire Formula Four as well, some 53 but not a whole lot else.
If we had a bit more broad scope, it would be 8.25 through 8.38, 8.5 to 8.75 (mostly skipping 8.6 though) and wheels 52, sometimes 53 but more commonly 54 mm, with the occasional 56 or bigger, but not too many now. For some reason people just don't like 55 mm wheels - can't move those things at all, even in good shapes and graphics.
Just to add, trucks - pretty much Thunder 148 and 149s in various styles, but Indy and Venture are also in there, mostly in the 8.25 and 8.5 widths of all trucks really. People even ride 149s on 8.75 boards a fair bit too, even though I have the trucks match any board I am on, eg 159s on 8.75 boards.