The device (1) for creating hair bundle effects to a hair bundle (11) described herein comprises a first portion (10) movably joined to a second portion (20) by means of a connection (30). The second portion (20) is associated with a system (70) for bending a hair bundle (11) within a cavity (12) provided in the first portion (10). The system (70) for bending the hair bundle (11) consists of at least a first fin (71) and of a second fin (72). The free distal edge (712) of the first fin (71) points toward the free distal edge (722) of the second fin (72). The device (1) preferably comprises a first metering layer (81) and more preferably also a second metering layer (82) to achieve evenness during the application of a hair treatment composition (15) to hair.