There are many types of straws, with pros and cons to each. Here's the stats:
To pick a straw size, follow this graphic. Every straw size happens to be the perfect size for different kinds of mason bees. The larger the straw size, the more types of mason bees you have the potential to attract.
Follow these next few graphics to pick what material to use:
There you have it! I personally use paper smoothie straws because they're large & one of the best materials for the bees. You can definitely mix sizes, but I wouldn't mix plastic with paper.
I would not use plastic straws, unless I'm recycling old ones. There's no reason to invest in the least attractive type of straws, when you can buy their favorite types instead.