Abstract: An inflatable seal for sealing an annular space between two flange parts is formed by a hollow ring composed of elastic material. The hollow ring has a tubular cross-section with a peripheral wall and is provided with a connection for an inflation medium. The peripheral wall comprises, in at least one area of the tubular cross-section, a blocking element having a substantially larger cross-sectional dimension than the remaining part of the peripheral wall. Furthermore, a set of flange parts and a container comprising such a seal, and a method of manufacturing such a seal are disclosed.