R17d HO tubes are common in 8', but did you know there are 4' and 6' fluorescent lamps that come with the R17d/HO base? Check out Keystone and Satco's options for 4', 6' and 8' R17d lamps. There are also some that are designed specifically for signs that come in the R17d base. All these options are Type B ballast bypass style.