noun which may take the genitive case particle 'no'
large size; large portion
Used as a modifier for items, servings, or products that come in a larger-than-standard size. Common in menus and product descriptions.
ラージサイズのポテトをください。
I'll have a large-size fries, please.
このTシャツはラージサイズしか残っていません。
Only large-size T-shirts are left.