From Team Fortress Wiki
Strange Filters are exclusive tools that are obtainable from the Mann Co. Store. Strange Filters can only be used on Strange weapons. Adding a Strange Filter to a weapon restricts the tracking of a statistic to a certain map, and adds an extra prefix to the weapon depending on which map the Strange Filter was for. All revenue from purchasing a Strange Filter, minus net taxes, is given to the map contributor.
Choosing to restrict the tracking of a Strange Part-related statistic may not award the additional prefix.
- Added Strange Filter items to the Mann Co. Store to support community map makers.