Although the RAE recommends that words ending in vowel + -l, -r, and -n  should take -es in plural, in practice many of these are seen spelled and pronounced invariably or with just a final -s.

-un pan → unos panes [Spanish word; normal rule]

-un bol → los boles [Often seen:'los bols']

-un máster → los másteres [Often seen/pronounced: 'los máster' or 'los másters' -read more]

-el tráiler → los tráileres [Often seen: 'los tráilers']

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