How is the esraj different from the dilruba?

The esraj is described as a variant, some say the modern variant, of the dilruba. Its body is smaller, rounder and shallower in the middle, while the dilruba has a flat, sarangi-like body, a broader fingerboard and more sympathetic strings. The dilruba is associated with Punjab and Sikh devotional music; the esraj is used in Punjab and also in West Bengal and Bangladesh.