handful, handfuls

  edgood  —  Grammar Tips
The proper plural is handfuls, not handsful.

Consider this usage note from Dictionary.com.
The plurals of nouns ending in -ful are usually formed by adding -s to the suffix: two cupfuls; two scant teaspoonfuls. Perhaps influenced by the phrase in which a noun is followed by the adjective full (both arms full of packages), some speakers and writers pluralize such nouns by adding -s before the suffix: two cupsful.

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