A process for producing a crosslinkable silyl group-containing polymer which is excellent in oil resistance, heat resistance, weatherability, low staining properties, and compression set characteristics, includes the steps of radically polymerizing a vinyl monomer in the presence of a thiocarbonylthio group-containing compound with a specific structure, and introducing crosslinkable silyl groups. The advertisement is specifically directed towards the recipient of the package. A resilient member is located between the valve stem and the valve member.