Filtering facepiece (dust masks) are generally made directly from a cloth-like filter material. Chemical cartridge/gas mask respirators can be made from a variety of materials. The most popular facepiece materials are silicone, neoprene, and rubber. In general, rubber and neoprene are rigid, durable materials. Silicone is usually preferred for its comfort, flexibility and ease in cleaning. Full-face respirators are available with strap harnesses or ratchet suspensions. The harness type can be worn under a hard hat, but ratchet suspensions are generally easier to adjust, making donning and doffing easier.