Genuine Bosch Sealing Disk — part number 1609201663 (also shown as 1.609.201.663). A small, precision sealing washer used in Bosch wet/dry vacuum assemblies to maintain the intake/motor seal and prevent loss of suction; it’s supplied as a single original Bosch replacement and is made to the same fit and tolerance the machine was designed for.

Typical fitment (examples): GAS 25 / GAS 25 L SFC, GAS 50 and several GAS 1000 / GAS 10‑50 variants (check the type number on your machine — e.g. 0601979xxx — to confirm exact compatibility).

Notes for repair: this part is a single sealing disk/washer (replace if cracked, flattened or perished) and sits where the hose/adapter or internal flange needs a tight seal; swapping it restores proper suction and prevents leaks. The part is listed among Bosch power tool spare parts under the same part number formats 1609201663 and 1 609 201 663.