This is a NEW chrome plated steel seat post. The color is silver. The diameter at the top of the seat post is 7/8". The clamp on all new seats fits this post. Almost all seat posts are 7/8" in diameter at the top where the seat clamps on, but some older bicycles have a smaller diameter at the top than this, so measure your old seat post at the top if you are not sure that it is the standard 7/8" diameter (you will need to take the seat off to measure the diameter of the top of the post).
The diameter of the bottom part of this seat post (the part that goes into the frame of the bicycle) is 25.4mm which is one inch. The length is 12". Almost all seat posts have the same diameter at the top of the post, but there are several different diameters of seat posts at the bottom part of the post. So, you will need to measure the diameter of a post that fits your bike to be sure that this post will fit. See "How to measure the diameter of a seat post" below.
>>HOW TO MEASURE THE DIAMETER OF A SEAT POST:
Close the jaws of an adjustable wrench on the seat post (the bottom part that goes into the frame). Then, measure the distance between the jaws. A more accurate way to measure the diameter of a seat post is to cut a strip of paper that will exactly go around the seat post, which will be the circumference. Measure the length of the strip of paper and then divide by 3.14. The number that you get will be the diameter of the seat post. If the circumference is 3.14" or 79.756mm, then the diameter is 1" or 25.4mm. If the circumference is 2.7475" (about 2 3/4") or 69.7865mm, then the diameter is 7/8".