OnePlus One sports a 5.5″ 1080×1920 JDI display. It’s powered by a 2.5GHz Qualcomm Snapdragon 801 processor and 3GB of RAM. Storage comes in at either 16GB or 64GB. Other features include a 13MP camera, 3100mAh battery, dual front speakers and StyleSwap replaceable back covers. On the software side, the OnePlus One runs a version of Cyanogenmod with a unique modified user interface.
Besides the Cyanogen OS, there are plenty of options available for the OnePlus One. OnePlus recently made Oxygen OS and even Hydrogen OS. Many custom ROMs are available for OnePlus One. One of them is SlimLP ROM. This ROM will update the OnePlus One to latest Android 5.1.1. A detailed guide to install this ROM on OnePlus One is given below.