URL: https://www.acorn.space/products/luna

Browser / Version: Firefox 57.0
Operating System: Mac OS X 10.12
Tested Another Browser: Yes

Problem type: Design is broken
Description: The quantity selector shows arrows while WebKit/Blink family don't
Steps to Reproduce:

1. Go to https://www.acorn.space/products/luna
2. Reach the quantity selector.

Expected only + and - signs, like on WebKit/Blink browsers.
On Firefox the widget for quantities show.

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