The gauge to front flare ratio for each size is listed below:

6g: 9.6mm tall x 10.75mm wide
4g: 10.6mm tall x 12mm wide
2g: 12mm tall x 13.6mm wide
0g: 14mm tall x 16mm wide
00g: 17mm tall x 19mm wide
7/16": 19.8mm tall x 12.25mm wide
1/2": 21mm tall x 24.5mm wide
9/16": 25mm tall x 29mm wide
5/8": 27.2mm tall by 30.8mm wide
3/4": 31.5mm tall x 36mm wide
7/8": 35mm tall x 40mm wide
1": 41mm tall x 46mm wide

These are really front heavy in most sizes and may require o-rings to stay in place.