The cap definitely adds warmth and is easy to use.  It is snug and fits uniformly to my head.   Without the cap, my ears would turn bright red from the cold.  With the cap, the parts of my head that are covered are quite comfortable.   The only negative is that the strap is a tad tight on my throat.  I haven't tried others and will continue using this one.

for females it is a little too big, but when used with a silicon cap over the top it really holds the heat.

Identical to Blueseventy Skull Cap  which I also bought.
Lack of adjustable neckstrap makes it cheap to produce but result is inferior comfort.

I used this recently swimming in Lake Michigan near Traverse City. Water temps have been unusually cold this year. The neoprene cap made a difference, keeping my head warm and comfy even in high 60's water.
I wonder about its durability, but time will tell on that.

Comfy and warm, what more could you ask?

too tight....