Examples of anaesthetic breathing systems that are commercially manufactured. From top to bottom: a Mapelson C system manufactured by Intersurgical; a Mapelson E system (also known as Ayre's T-piece), to which a Venturi valve has been fitted so as to reduce the delivered oxygen concentration; and a Mapelson F system (also known as the Jackson-Rees modification of Ayre's T-piece) manufactured by Intersurgical.
<a href="//commons.wikimedia.org/wiki/User:Kwekubo" title="User:Kwekubo">Kwekubo</a>
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<span class="int-own-work" lang="en">Own work</span>