Progressive release bases are designed to flex and absorb energy as a player slides into the base. In the case of a short slide, the "progressive release" action allows the base to flex until enough force is applied to "pop" the base free from its mount. Molded from a durable cut-resistant polyurethane. Molded 7" stem fits into a ground mount. White side is anchored in a ground mount that is provided. Orange side is anchored under base with hammer-in spikes that are provided. Wt. 17 lbs.