SRL for [constrains]: The softness of the core [constrains] the plastic models to No . 1 , No . 2 or No . 3 - type pencils , which account for the bulk of the market .
ARG-0: The softness of the core | ARG-1: the plastic models | ARG-2: to No . 1 , No . 2 or No . 3 - type pencils , which account for the bulk of the market