| 521 / | HD | SYNTHETIC RESINS OR NATURAL RUBBERS -- PART OF THE CLASS 520 SERIES |
| * | DD | SYNTHETIC RESINS (Class 520, Subclass 1) {3} |
| 50 | DF | .~ CELLULAR PRODUCTS OR PROCESSES OF PREPARING A CELLULAR PRODUCT, E.G., FOAMS, PORES, CHANNELS, ETC. {27} |
| 142 | DF | .~.~ Cellular product derived from ethylenically unsaturated reactants only {5} |
| 146 | ![]() | .~.~.~ From aromatic reactant {2} |
| 147 | DF | .~.~.~.~> With oxygen or nitrogen containing reactant |
| 148 | DF | .~.~.~.~> With conjugated diene reactant |