Use this simple adaptor to turn your Sawyer filter into an inline filtration system for your hydration pack with this simple accessory. Compatible with the Sawyer Squeeze Filter and the All in One Filter. Your filter can easily be removed and re-attached to your Hydration pack as required. This system is currently in use with UK Special forces, and several other Military units around the world. NATO STOCK NUMBER - NSN 4730-17-924-8946 NOTE: This adaptor is suitable for use with SP131, SP129, and SP181 type filters only.