The good feet store maintainer mid flex size large. 357. The Good Feet Store Maintainer Mid-Flex (Size 4-357) is a firm yet flexible, 3/4-length orthotic insert designed to support all four arches, providing pain relief for conditions like plantar fasciitis, while offering more comfort than "Strengthener" models. These black arch supports feature a lower-profile design, making them suitable for athletic, casual, and dress shoes. Key details about this product: Function: Designed for daily, long-term support (maintenance) to improve posture, balance, and relieve pressure on feet, knees, hips, and back. Flexibility: "Mid-Flex" offers a balance between support and flexibility.