Lidocaine acts as a local anesthetic wherever this patch is applied. HealthWise Pain Relief Patch with 4% lidocaine can be applied wherever pain relief is needed – back, arms, shoulder, legs and knees – for up to 12 hours of relief. Includes: 12 individually wrapped patches per box; 4 small 4.72” x 3.14”; 4 Medium 7.87” x 3.93”; 4 Large 984” x 5.51” with detailed instructions and warnings. Can be used up to 12 hours, no more than 2 applications per day. Intended for adult use only; use for children under 12 should consult with a physician before use. Dedicated Customer Care Help Line for end-user product inquiries.