I live in a co-op apartment in the Bronx, NY. When we purchased the apartment, it had three good sized old radiators that actually created too much heat. I found replacement radiators at www.steamradiators.com and purchased three units. The units I have are 18" x 36" x 1". The pipes on them are 1". The steam pipe is 1 1/4". Therefore, several plumbing parts were necessary including a handle to open and close, a reducer to get to 1", a small length of pipe and a few nibs. Using teflon tape and a sealer called Grripp, and with the help of a plumber who placed the shutoff valve on the steam pipe, I was able to complete both jobs and install them on the wall under the windows.
I feel that these are excellent alternatives to conventional steam radiators. They come painted and once installed look pretty nice.