The ""L"" designation indicates a linear bulb, Bulbs in the L-Series are either in the LB Group or the LF Group, ""LB"" designates linear bulb with bi pins, or connecting points at both ends of the bulb, T5 Bi Miniature (15mm) has 2 brass connecting Bi-pins at each end of the bulb, Bulb is 15mm wide, SKU: PENT084