Concrete forms stand strong as the most economical way to create round columns for buildings, entryways, structural columns, light posts and other commercial and residential structures. Ring's End Full-Service locations stock 12 ft. lengths, and select Ring's End locations stock 4 ft. lengths as well. 8 in. x 12 ft. construction tube, requires approximately 48 lbs dry concrete mix (before adding water) per foot of height.