On the specification page of ASUS website for gl552vw, it says...
- 1TB HDD 7200 RPM
- 1TB HDD With 128 G SSD SSD (M.2 2280)
However the variant cn426t is not specifically elaborated. From the above specs, it can be assumed that the motherboard of all gl552vw variants has a M.2 slot. However the only entity that can confirm is ASUS itself.
The best way would be to call up ASUS customer support and confirm with them. If they confirm you have a M.2 slot on that specific model, you are good to go.