Panel with locking device

A set of panels comprising a first panel, a second panel and a mechanical locking device for locking the first panel to the second panel, the mechanical locking device being configured for an assembly by a displacement of the second panel in relation to the first panel in a vertical direction to obtain a locked position of the first panel and the second panel, wherein the first panel comprises a first edge, a first panel surface and a second panel surface and the second panel comprises a second edge,

• wherein the mechanical locking device comprises a locking strip extending from the first edge in a direction parallel to the first and second panel surfaces,
• wherein the locking strip comprises a locking strip edge,
• wherein the locking strip comprises a first locking strip surface extending in a direction substantially corresponding to the direction of the first panel surface of the first panel,
• wherein the locking strip comprises a second locking strip surface extending in a direction substantially corresponding to the direction of the second panel surface of the first panel,
• wherein the locking strip comprises a locking element configured to cooperate with a locking groove at the second edge of the second panel for locking in a direction parallel to the first panel surface,
• wherein one of the first or second edge comprises a tongue configured to cooperate with a tongue groove at the other one of the first or second edge for locking in a vertical direction,
• wherein the mechanical locking device comprises a flexing groove extending from a transition between the first locking strip surface and the first edge and into the first panel at an oblique angle from the first panel surface, wherein the locking strip is configured to flex by varying a shape of the flexing groove during the assembly,
• wherein an opening of the flexing groove that is connected to the first edge is positioned at a distance A1 in the vertical direction from the first panel surface,
• wherein the flexing groove extends a distance A2 in a direction essentially perpendicular to the second panel surface, and
• wherein a ratio between the distance A2 and the distance A1 is about 0.3 to about 1.2.