New textfield editable like description field

[obtgrafi]

Hi,

I've hanged my product display page and I use tabs. First tab conatains product descripiton and secon is filled with form "Ask a question about product". I want to add third tab - product dimensions.  Is it posible to add custom field "dimensions" which will be editable like product description on back end? If I add a fileld type "string" it displays only one small editable input box.

Maybe somebody solved this problem.