21 Single Spring seal and there are series 0.5"-4".It's popular model which are widely used for many kinds of water pump.Replace John Crane Type 21 with "N" seat
Operating Limits:
Pressure: 0~1MPa
Speed: ≤13 m/s
Temperature: -30ºC~+200ºC
Rotary Ring(Carbon/Sic/TC)
Stationary Ring(Ceramic/Sic/Tc)
Secondary Seal(nbr/Epdm/VITON)
Spring & Other Parts(S.S/Sus304/Sus316)
Design Feature:
a. Single spring,rubber bellows seal.
b. Besides the stationary ring of type "N" ,other stationary rings
such as John Crane types "W" , "WM" can also be provided.