I guess he means standard sizing
Type-I (Heavy) - Skycrane / S-61 / 214ST
Type-II (Medium) - Bell 205
Type-III (Light) - Jetranger / Md-500
Helicopter Classification per USFS:
Type I, Heavy: 700 gal water, 16 seats including the pilot, allowable payload 5000 lbs. (e.g.: Boeing-234, S-64, AS-332, Vertol-107)
Type II, Medium: 300 gal water, 10 seats including the pilot, allowable payload 2500 lbs. (e.g.: Bell-212, Bell-205, BK-117, S-58)
Type III, Light: 100 gal water, 5 seats including the pilot, allowable payload 1200 lbs. (e.g.: Bell-206B-III, 206L, Lama, MD-500, AS-350)
Type IV: 75 gal water, 3 seats including the pilot, allowable payload 600 lbs. (e.g.: Bell-47, Hiller-12E)
In the medium category, we operate a Huey, (restricted) and a Bell 212 which can be fitted with a tank, and has rappel brackets. It comes down to personal choice I guess...