Можно собрать и на пластиковых толстостенных трубках, на оборудование Тetra Pak так сделана система смазки. Диаметр 5-6 мм, обжим такой же как на металлических через бронзовое колечко. Есть прозрачные, вбейте в яндекс “систем централизованной смазки смазки фитинги трубки”
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