Is the polarized version worth paying the extra money? Not sure if I should buy the one with regular lens or the polarized ones.Which one is better?

Depends on what your going to use them for, if you wanna use them for fishing or like seeing fish in the water,skiing or other outdoor sports get the polarized. If not save your money. Having polarized lenses will make it tougher to to see Electronics that use led lights and lcd screens. This article should help make your decision. But for how cheap these sunglasses are spend the 10 bucks on the non polarized and 20 on the other,you can have one of each and get your free shipping. http://www.allaboutvision.com/sunglasses/polarized.htm

What's the actual size of these glasses? Can anyone tell me the measures in centimeters?

They're actually pretty small. 13.4 cm wide and 3.6 cm tall.

Can you get these polorized kd's in blue lenses?

They do not make a blue polarized lens in either the original KD's or the larger X-KD's. The parent Company Pacific Coast Sunglasses has 2 models with blue lenses that are polarized sunglasses in their Kickstart brand - the 6402 and 4222.

100% uva and uvb protection?

According to the Pacific Coast Sunglasses website they have 100% UV protection. And they are polarized! These are great sunglasses at an amazing price.