Nexus 5 is powered by a powerful Qualcomm Snapdragon 2.3GHz quad-core processor, 2GB of RAM and an Adreno 330 GPU. The 4.95″ True HD IPS Plus display has a resolution of 1080 x 1920, with a pixel density of 445 ppi. Storage comes in at either 16GB or 32GB. Other features include an 8MP camera, LTE connectivity and a 2300mAh battery.
Nexus 5 has received Android 6.0 Marshmallow. However if you are not a fan of stock ROM and prefer custom ROM, then you can switch to CM 13. CyanogenMod team have released an official nightly of CM 13 for Nexus 5. Follow the below guide to install it on Nexus 5.