"20 foot cable" or "20 feet cable"? (WHICH IS CORRECT?)

Depends somewhat on context/ usage.

These are both correct:

"Use a 20-foot cable to attach the thingamabob to the doohickey."

"That cable is 20 feet long."

You need to hyphenate the number and measurement for it to be correct, though.

I'm going with "feet".

Doesn't it sound a little funny to say,"This is a 20-feet long cable"?

But it doesn't sound funny to say "This cable is 20 feet long".

Buffalo, note the constructions I used.

"This is a 20-foot cable."

OR

"This cable is 20 feet long."

Your title asks "'20 foot cable' or '20 feet cable'? (WHICH IS CORRECT?)"

Of those two sentence fragments, "20-foot cable" (with hyphen) is more correct.

If you add the word "long", as you do later, then the way to say it is "This cable is 20 feet long."

I think that the correct way is:
A twenty feet long cable
or...
A twenty foot cable

Not sure if i'm right, just a speculation

Adjectives should not be used in plural form.

2-car garage.
20-foot cable.

Thank you, Sozobe and Craven. This is easy for me but difficult for some, and I think you have both given clear and correct help!

Eskimo, you're right when you say "twenty-foot cable" (except as Soz says, you need the hyphen), but you're using the same part of speech (adjective) when you say "twenty-foot-long" - that is, the phrase "twenty-foot-long" describes "cable".

The time to use the plural "feet" is when you are NOT using "twenty feet" as an adjective. In the sentence "The cable is twenty feet long" the phrase is, I think, a predicate phrase telling what the cable "is"...

It's been a loooong time since grammar class. I'm sure of the construction, just not of the terminology...

Wy, that's what I have the biggest problem with, too. I know what looks right and what looks wrong but know very little about the terminology needed to explain it. Craven said "adjective" and I said oh, that makes sense, but hadn't thought of that until he said so.

i went with foot because of an old expression, i wouldn't touch it with a ten foot pole--Ronald Reagan used it, so it must be correct, right?--but it's good to know that the phrase is gramatically correct.

After searching and reading every ones opinions on this mater I came across an answer I believe is correct. In this forum here http://www.englishforums.com/English/FeetFootDistanceMeasurement/dwb/post.htm The last answer to the foot or feet question stopped the forum in its tracks. The answer was (Foot is correct. It is both the plural and singular when referring to measurement (1 foot, 100 foot, 1000 foot tall/high/wide etc). Feet are the two things on the end of your legs. Many people erroneously use 'feet' as a plural in this context and consequently get themselves into a muddle with certain sentences (and sound like a 4 year old for the rest of the time).)

On this mater? Whose mater, yours? The wife of your pater? You've lost me here.

He doesn't seem to have graduated from an alma mater..

Alma was his mom?

King Charles II was a randy cocksman, and he had many bastard children. Those whose mothers were of the aristocratic class got titles and incomes. But one of his long-time lovers was the former actress and "orange-seller" (i.e., hooker) Nell Gwynn. A few years after the birth of her first son by him, Charles Beauclerk, she started calling "you little bastard" whenever she was in the presence of the King. It finally got on Charles' last nerve and he asked her why she kept calling him that. Nell replied that he hadn't any other name. Soon thereafter, Charles created him Earl of Burford and gave him an income.

During the anti-Catholic rioting Nell's carriage was stopped by a mob as it left Whitehall Palace. Nell leaned out and said something to the effect of "Gentle, good people, this is the Prostestant whore." The crowd had a good laugh, and saw her safely on her way.

They just don't make kings and queens as they used to do . . . nor maters and paters, either.

Does that matter?

No, it's just idle patter.

I used to deliver newspapers to Nell Gwynne's house. They now restore Mosquito aircraft there.

http://en.m.wikipedia.org/wiki/De_Havilland_Aircraft_Heritage_Centre