Key structure for keyboard

A key structure for a keyboard, the keyboard having a top plate, and the top plate being provided with an insertion opening, the key structure comprising:

• a lower shell inserted into the insertion opening, wherein an annular stopper protrudes from of the lower shell and the lower shell comprises two transparent grooves arranged on two opposite inner sides of the annular stopper, the annular stopper is formed with two elastic arms on outer sides of the two transparent grooves, two clamping hooks engaged with the top plate extend downwardly from the two elastic arms, the annular stopper is exposed on the top plate, and the annular stopper and the top plate stop and locate each other;
• an upper shell assembled above the lower shell, wherein the upper shell comprises a through opening;
• a pressing shaft movably disposed between the lower shell and the upper shell, wherein a top end of the pressing shaft penetrates the insertion opening;
• and
• a spring disposed and elastically supported between the lower shell and the pressing shaft.