I think you've answered your own question there Piotr. Never heard of Seaflex, Teleflex/Seastar is the dominant brand here in the uk, spares are readily available & I've never had any problems.
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Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4:Don't feed the troll
Same in the US. Ultraflex is a distant second to Teleflex/Seastar. Might be a third one, but I can't think of the name (which is somewhat telling in its own right.)