WPS Product of the Month The best products from the best brands, hand-selected by our experts. See the product everyone is talking about this month right here! Havis Self-Adjusting Double Cup Holder Self-Adjusting Double Cup Holder. Self-adjusts to fits cups up to 3.5" in diameter. Click here to see all variations of this best seller! Internally mounted dual cup holder. Self-adjusts to fits cups up to 3.5" in diameter.