I'm planning to buy HOYA and x400 Filter?

I'm confused on the size of the filter. I have Nikon D5100 and the lens i have are 18-55mm and 55-300mm. So what size i have get 55mm, 77, 58, 67 or 62mm someone please explain and suggest me the size.

Look on the inside of the lens cap, or the very front of the lens where it will tell you. The 18-55 is a 52mm filter thread, I don't know what the 55-300 uses.

This is an expensive specialist filter, therefore I would generally advise that you buy the largest size available and use step down rings. It may be more expensive in the short run, but does mean that you then don't need to shell out again in the future for larger filter sizes.

Your 18-55mm is 55mm, and your 55-300mm is 58mm (according to DPReview).So you'll want 77-55 and a 77-58mm rings and a 77mm filter.