Hanover manufactures two types of Roof Ballast Pavers - Standard Pavers for Walkway and Ballast and Lightweight Ballast Pavers. The Standard Ballast Paver is stocked in a Natural color and a non-slip Diamond finish. A wide range of sizes are available. Unlike river gravel which has been known to be hazardous, pavers used as ballast or walkways provide a durable, safe method of protecting the roof system.