Light machine oil like sewing machine oil should be applied regularly to all of the smooth axis rods on your printer to keep everything in smooth operation.
Spring used in the build plate assembly for the Ultimaker 2 series and Ultimaker Original+ printers.
Official UltiMaker spare part for the following machines:
Ultimaker Original+
Ultimaker 2
Ultimaker 2 Extended
Ultimaker 2 Go
Ultimaker 2+
Ultimaker 2 Extended+