Seals with a metal case generally have the most OD interference, or ability to stay put inside the housing. The trade-off for this tight fit is that housing damage might occur when a metal case seal is installed. Some customers prefer a rubber OD seal for this reason, as it will not scratch or damage the housing during the installation process. Another consideration is that standard steel metal cases might oxidize or rust over time, and this would not be a concern with an all-rubber or metal-encapsulated rubber OD seal.