Merrell All Out Terra Light Synthetic Air Mesh/TPU upper - Offers durable, yet breathable coverage. Synthetic Overlays - Wraps the foot for a secure fit. Synthetic Leather lacing system - Provides a secure fit. Bootie Construction - Acts as a partial gaiter to keep debris from getting inside the shoe and secures the heel when running through deep mud. Toe Guard - Extends from the outsole to provide protection against rocks and debris.