Gas Lens Insulator 53N66.
(ref. Row 6 of table below.)
Insulators protect the torch consumables from high heat, and create a seal between the nozzle and the torch. Helps prevent leakage of shielding gas.
For other accessories suitable for WP-24 (A-80) type TIG welding torch, please see here.
Click here for a reference of the original torch model.