Radiator valves question plumbing advice

Radiator valves question Hi guys, got supplied some corner valves but they have a rubber to go into the radiator inlet to create a seal.

Well I imagine that's the idea, fit hundreds of valves but always used Ptfe or Loctite. Never actually seen one like this.

Will the rubber do the job, or should I remove and fit as normal with Loctite?

Any advice be appreciated

Thanks

Radiator valves question to read more on the original thread at Plumbing Advice

See also UK Plumbing Advice for all UK plumbing advice needs.