In Powerlifting meets, records can be set by as little as 1/2 a kilo over the previous record.  When the smallest regular plate is 1.25 kg, how can you do this?  You need to have as set of the "record plates" or "chips" as they are often called. 

Since a record lift can be set at any 1/2 kilo increment, meaning .5, 1.0, 1.5, or 2.0 kg, you need the correct plates to do that, so 2 pairs of .5 and  1 pair of .25 kg plates are required to make any increment.  This set includes that.