A non-powered device intended to be applied with or without pressure to the body surface (i.e., non-invasively) to provide heat and/or cold therapy for the skin and/or underlying tissues in the treatment of musculoskeletal pain and discomfort (e.g., from sports injuries or rheumatism). It consists of a compact envelope filled with a thermally-retentive material (e.g., silicate-based gel) that can be heated and/or cooled. It may be shaped/sized to fit a specific anatomy or include a strap; it is not intended to support the neck, nor is it designed to be dedicated to eye thermal therapy. This is a reusable device.