The Canon Gelatin Filter Holder IV is for 4x4" (100x100mm) gelatin filters.
To use this holder you must purchase an adapter that matches your lenses filter size. Available adapters are: 52mm (2714A002), 58mm (2715A002), 67mm (2716A002), 72mm (2712A002) and 77mm (2713A002).
An optional hood is also available (2695A002). Multiple hoods can be "stacked" to increase the length for telephoto lenses.