Small wedge is 15.5 cm (6"), for ratchet wheels and benches.
Large wedge is 19.2 cm (7.75"), for loom beams. Most of the main parts of the loom use the large wedge.
If a wedge falls out of your loom, be sure you put the wedge back in the correct direction. Take note that the mortise is tapered and the wedge needs to fit snugly with no gap where it exits the square hole. Putting wedges into your loom parts from the wrong direction can result in damaging your loom. It is also best to put the flat grain part of the wedge towards the body of the loom.