These 4" x 4" self-adhesive First Aid Kit Inside labels are made from outdoor-grade vinyl and feature a super-tough, smear-proof lettering that will stand up to years outdoors or in tough industrial environments. The mounting surface must be clean, dry, smooth and non-porous (brick, cement block etc. is porous; third party adhesive may be needed on such surfaces). A good companion label is item # 09383.