Johns Manville Spin-Glas® WHXG / Range-Glas® XG is a lightweight, highly resilient fiberglass insulation manufactured using rotary-process. Spin-Glas WHXG / Range-Glas XG is designed for use in ranges, ovens, residential and commerical water heaters (both electric and gas), provides superior thermal and acoustical performance and is available in a broad range of densities.