Below you will find our suggestions for the best hiking shell layers. The main function of a shell layer is to provide protection against the elements (rain, snow and wind). A shell (outer layer) is usually worn over the mid-layer and base layer. In warm weather the shell can also be worn directly over the base layer because insulation is not required. Shell layer garments include rain jackets, softshell jackets and some insulated jackets which are also waterproof or water-resistant.