The original BBS RS center caps were produced in more than one size, and choosing the correct one depends on the exact wheel model. That is why two wheels can both be genuine BBS RS, yet use completely different cap hardware.

RS Classic center caps were split into two main families: 

-small-thread 58 mm version and

-large-thread 72 mm version.

The small-thread setup uses nuts 09.24.001 and 09.24.002, which are the 30 mm and 20 mm high versions, together with logo 09.23.221 and waffle plate 09.24.038.

The large-thread setup uses nuts 09.24.003 and 09.24.004, again in 30 mm and 20 mm heights, paired with the same 09.23.221 logo, and most commonly waffle plate 09.24.028.

The larger 72 mm cap family was not limited to just one waffle plate design. BBS also listed a second large-thread assembly, 09.32.007 / 09.32.008, which keeps the same 72 mm ring 09.24.014 and the same tall and short nuts 09.24.003 / 09.24.004, but uses plate 09.24.069 instead of 09.24.028.

Among restorers and sellers, this less common plate 09.24.069 is commonly referred to as the rarer 15-weave / 15-wave plate, while 09.24.028 is the more common large-thread RS waffle plate found on most 16-inch, 17-inch, and some 18-inch RS wheels. 

Because of that, for identifying the correct BBS RS center cap it is the best to check the  measuring the outside of the waffle plate. You also need to know the thread size, nut height, and in some cases even the waffle pattern itself.

To conclude:

The 09.24.038 plate is sold with the 58 mm hexagons for small-thread RS waffle for most 14-inch and 15-inch RS wheels, with some small-thread 16-inch exceptions such as RS003. The common large-thread 09.24.028 is roughly 170–171 mm in outer diameter, with a 72 mm opening, and is described as fitting most 16-inch and 17-inch RS wheels.