Question about Vengeance LPX - 372965

Hello, I bought this 16GB pair to complete another 16GB pair. But this one display only 2133MHZ instead of the expected 2400. CMK32GX4M2A2400C14 -> display 2133 MHZ My previous pair is CMK32GX4M2A2400C16 -> display 2400 MHZ as expected What the difference as the description is the same (other one is a bit more expensive and out of stock, search for CMK32GX4M2A2400C16) Best!