New Polar WearLink Transmitter is now available for purchase as an accessory. Compatible with all Polar monitors. The slim and light Polar WearLink coded transmitter is compatible with S510, S520, S710, S720i, S725, S725X, S625X, CS100, CS200, CS300, and CS400 (compatible only with the coded transmitter). This is because the cycling features speed and cadence sensor need to have the coding feature. Sizes: M – XXL and XS - S