I just recently installed Zen Cart 1.38. One of the default product characteristics is "Product Weight" with default unit of "lbs". Now I want to change "Product Weight" to "Unit Size" 'cause our products' unit is either "mili-liters" or "mili-grams". The product weight is default defined as number with default unit of "lbs". The thing is how I can modify the parameter "Product Weight" to be text rather than number. Help will be greatly appreciated.