You can use even a 3000 MHz DDR3 on your motherboard, it's up to your memory controller to handle that speed.
If your memory controller only supports up to 1333MHz, the 1600 MHz will work at 1333MHz. That also applies to the 3000 MHz RAM, you put them and they will low down to 1333MHz, simply because that's the maximum supported speed.
You can use even a 3000 MHz DDR3 on your motherboard, it's up to your memory controller to handle that speed.
If your memory controller only supports up to 1333MHz, the 1600 MHz will work at 1333MHz. That also applies to the 3000 MHz RAM, you put them and they will low down to 1333MHz, simply because that's the maximum supported speed.
My ram was on 1333mhz when i installed it but the website of corsair says that my RAM is "tested" for 1600mhz so I was a litlle confused , that´s why im asking if it is safe (for the ram)