Canon 52mm Drop In Screw Filter Holder II

Accepts standard 52mm filters. Compatible with: EF 300 f/2.8L IS, 400 f/2.8L IS, 500 f/4L IS, 600 f/4L IS II USM Lenses. The enclosed regular filter can be exchanged with other commercially available screw-type filters. Note that only filters with correct filter frame thickness can be mounted on the lens.

Price: 119.99 from Wex Photo Video