Genuine Casio G-Shock watch band posts and screws, two of each, for the following models: 

GW-500A      GW-500E      GW-500J     GW-500U     GW-500WCE  

GW-501    GW-510A    GW-510J    GW-520J     GW-530A    GW-M500A

GW-M500BA    GW-M500F   GWM-530A 

The length of the posts are slightly different at the 6:00 and 12:00 hour positions, the package will be clearly marked.

Note: The picture of the watch is for reference only.