Zeppin Spring Gauge for RC racers.

 

Springs do not make equal and degrade over time, this tool measures spring tension to differentiate spring hardness. Four measurement units can be display N/mm, N/cm, LB/in, gf/mm.

Optional shim set for measuring small spring such as 1/12 pan car spring, 1/10 F1 : https://www.ebay.com/itm/355287068474