As of March 17, we are out of inhouse stock, but have more serial numbers on form 3s so this is backorder-ok. The octane 45K is identical to the full size octane except in length (and a more grey finish). Its shorter so you lose a little suppression but it is in the "who cares" level of difference for most people, especially if they prefer the shorter length. On medium to 16" barrels you may not have any practical sound difference if the barrel is long enough. The 45k is very popular with 3 lug use.