Shells from a shell chest and after usage will give out a random stats shell which can be use to slot into an equipment and weapon. Shell come at different level the higher the level the greater the status. Shell can be synthesize to acquire a higher level shell. Shell can be found in a tab next to backpack
Shell can be put into slot of equipment, Blue equipment has 3 slots while purple equipment has 6 slots. Same type of shell cannot be imbedded into the same equipment.
It require 2 of the same type to be synthesize into a higher level of shell. Higher level of shell has a higher set of status.