Jackson Rees T-Piece Circuit with 0.5L open tail bag 1.8mJackson Rees' modification of the Ayre's T piece (alternative name Mapleson F system) connects a two ended bag to the expiratory limb of the circuit, gas escaping via the `tail' of the bag. This allows respiratory movements to be more easily seen and permits intermittent positive ventilation if necessary. Intermittent positive pressure ventilation may be performed by occluding the tail of the bag between a finger and thumb and squeezing the bag. 0. 5L