Is this compatible with Ryzen 7 1800X?

It should be but best way to know is to check the motherboard of the manufacture and see if compatible as not all memory is compatible with all motherboards.

What motherboard / cpu combination can use this right now ?

As of now the only motherboards that support this are the new X99 motherboards for the Intel Haswell-E line of CPUs, which are Socket 2011-3.

What is the Timing on this stick?

It's the standard CL15 timings... 15-15-15-39.

Questions & Answers: Crucial 4GB DDR4 2133 (PC4 17000) Desktop Memory Model CT4G4DFS8213

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Crucial 4GB DDR4 2133 (PC4 17000) Desktop Memory Model CT4G4DFS8213

DDR4 2133 (PC4 17000)
CAS Latency CL15
Voltage 1.20V

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