Shell

Also know as outline or outer perimeter, the shell represents the outer wall of a 3D print.

Used in plural (“shells“) in conjunction with a number to describe the maximum thickness given to the outer wall. Printing with 4 shells means that your objects’ outer wall will be 4 times your 3D printer nozzle’s diameter (i.e 4 X 0,4mm = 1,6mm outer wall).