These are the visible hubs of the kit's road wheels. Two layers of wheels are visible in the completed kit; the outermost ones (on the left of this photo) and the first inner layer (on the right of the photo).
The kit's designers have carefully reproduced the details of the Tiger's wheel hubs, but they made an error. As indicated in the photo, they believe that both kinds of wheel were attached by nuts threaded onto posts.
But the real Tiger wasn't like this. Its outer wheels were attached by nuts but the inner layer by bolts. The difference is visible in this photo.
There is a "fix" for this problem in the kit; you can sand down the bumps on all of the parts numbered "R3" so that they resemble bolt heads rather than nuts.
Note: the kit designers made exactly the same mistake on the "R2" wheels also, but you need not worry about those, because their hubs are invisible in the completed kit.