That is no typo, the 8GB Corsair Vengeance LPX kit which Hardware Canucks just reviewed is indeed 4000MHz effective at timings of 19-23-23-45.  The small size of the dual channel kit helps keep the MSRP to $225, affordable for what it is and not removing the purchase of a second kit from the realms of possibility.  However the question of performance remains, does a DDR4-4000 kit provide noticeable performance improvements or is it simply good for bragging rights for those few with a motherboard that can support it?  The results vary, especially when looking at memory timings and CPU overclocks compatible with the memory frequency however it was also clear that this memory could probably go faster … if you had components that were capable of reaching those frequencies.

"The Corsair Vengeance LPX DDR4-4000 is one of the fastest, highest performance memory kits around but with a capacity of just 8GB, will it be enough for today's applications? "

Here are some more Memory articles from around the web:

Memory