database

hi good day to everyone… i am developing an inventory system for my brother… the product they are selling are OIL , HARDWARE , TIRES… the fields of oil and tires are quite similar except in the hardware bcoz in the hardware example NAILS we cannot put 10 kilos of nails in the field of size instead kilo.. i make a table for oil and tires… but i cant include hardware bcoz of the kilos.. my questions shouls i make another table for a hardware… if answer is yes how should i manipulate it in a form ? if no how ? pls help me…. tnx