This item is obsolete it has been replaced with the HFR258 which is what you will be sent
https://www.easy-controlgear.com/products/philips-hfr258tld-ph-2x-58w-hf-regulator-ii-ballast-dimmable?_pos=1&_sid=078486bd3&_ss=r
This Philips HF-R 255 PL-L dimmable ballast runs 2 x 55w PL-L. This ballast's lamp power can be regulated from 1% to 100%, automatic stop start, automatic restart after lamp replacement, up to 75% reduction in energy consumption and quick programme flicker free start.The Philips HD-f ballasts are commonly used in offices. These units are for use with installations with emergency back up.