This is a RC wheel I've designed for an old Land Cruiser 7 series but there are some other cars that use it. It is 1.9" standar size, but has a positive offset of 3mm to get narrower axle look. It uses standar 12mm hex.
This wheel has been tested with stock Axial SCX10 knuckles. If you use different knuckles be sure they have similar design as SCX10 ones, or due to possitive offset the wheel could hit them.
You will need six 1.6mm screws to get the final scale look (I use 1.6x8).
NOTE: It has no hub cap, but a good option to get a great scale look are some Junfac hubs: http://www.junfac.com/shop/index.php?main_page=product_info&products_id=492
NOTE2: The wheel you see in the photo is not exactly this one. This newer version has better look and 6 screws instead of five (for printing limitations).