The SF-TF is a stainless stell spring developed by Lesjöfors. It comes with a right hand coiling and it is made from Dt 0.2010 following EN 10270-1-SM standards as well as Dt 0.2-2.0 following EN 10270-3-1.4310-HS standards. This spring has a tolerance of SS 2384 and a working temperature of at most 120 °C in EN 10270-1 standards and 250 °C in EN 10270-3-1.4310 standards. Furthermore, the springs with a Dt of at most 0.4 does not come with any ground end coil while the others come with 3/4 ground end coils. On the other hand, the springs with a Dt of at least 2.0 are shot peened.