I wear a cap under my helmet on every ride year round. It protects my bald beak from the sun. Also learned my lesson a few years back before I started wearing a cap when I got stung by a bee on the crown of my head on a very steep and fast descent off a mountain climb. Anyway, this cap is super light and breathable. You can easily tilt the brim when you need to without interfering with your helmet fit. The material wicks away sweat unlike the cotton caps. The SPF is a bonus. I look to buy a couple more to keep in my cap arsenal. If you want a cap under your helmet this one is the best I've had so far...and you should see my collection.
It seems like I've been on an endless quest for just the right winter shoe cover. One brand was cut too low and loose around the top, allowing water to run down my legs and into my shoes. A pair of GoreTex covers kept the water out, but didn't fit well -- way too much fabric, which seemed floppy and not aerodynamic. Castelli's Diluvio covers are like Goldilocks -- just right. It fits snugly over cycling shoes, providing a sleek, aerodynamic fit. It is ruggedly built, with serious reinforcement at the toes and around the heels. The neoprene is thick enough to provide warmth without being overly bulky and without overheating my feet. They sit snugly and well above over my ankles, and neoprene collars at the tops help seal out water on wet days. The hook-and-loop closures on the bottoms make it easy to put them on and take them off, and allow for easy custom fitting around whatever cleats you are running on your shoes. One word of caution, though -- like everything else Castelli makes, these tend to run small. There is no size chart on WBW's web page, so you'll need to check Castelli's site. I wear size 47 shoes, and a 2XL works well for me.
I purchased these booties to use on my MTB flat pedals because the picture of the bottom of these booties looked as though it could survive the rough pins on my pedals. Indeed, they have preformed admirably after a dozen outings. All other waterproof/winter-proof booties I have owned (many!) have always fallen apart because they are made only for clipless pedals and not MTB flat pedal. These booties are quite tight to get on (I ordered an XL pair for my 46 Shimano flat pedal shoes), but can just stretch enough to work. Clipless type shoes are narrower, so XL would probably fit larger shoe sizes in the clipless variety. The booties them selves work just fine..not totally waterproof on extremely hard rains and longer rides (2-3hr), but nothing I have owned is totally waterproof under such conditions. I gave these a four star rating only because I wish they were a bit larger for the type of shoes I wear. I am very glad that I purchased these booties and would gladly recommend them to any flat pedal, MTB users.
In 36-60deg F weather these over-shoes have kept my toes from freezing on descents (I get numb fingers and toes easily). They're small enough to store in my tail bag when things warm up and they slip on easily without issue.
As far as being waterproof, they're good enough for anything except the really wet days. If you're going over big puddles it seems that water can splash upwards into regular (summer) road shoes. On days with light rain, steady mist, and gentle showers they have been excellent and kept my feet dry.