The Zodiac Disc also known as a skirt sits just above the flexi foot on most pool cleaners, it requires replacing when the disc is sucked into the cleaner mouth or folds under itself while the pool...
The Zodiac T3 Washer Upper & Lower are to help securely fix the diaphragm assembly inside the main body housing of the pool cleaner and allow it to swivel.
The outer extension pipe for the T3 / T5 which holds the T3 / T5 engine together.
Note: Be careful when unscrewing this part as debris can be inside the thread and damage it.