If its really 12T when it was advertised as 15T, you should file a claim with ebay and get your money back easily. Select reason as “item not as described” and its a cut and dry case.
This kit was created and is sold from a member on the forums. The ebay listing is a rip off of his work with poor quality parts that don’t match the description.
If you want to buy the actual kit, and read up on what happened the thread is here.