The 1500 series has a more powerful 15W bulb and an inline ballast.  The linear fluorescent bulb means a longer light that illuminates a larger area than the 1300/1400 series.

Approvals: cULus

Part No. Watts Bulb Ballast Lumens Cord Dimensions
LE1525 15 Linear Inline 920 25' 22" L x 2" dia.
LE1550 15 Linear Inline 920 50' 22" L x 2" dia.