NIV  Not only so, but we also rejoice in our sufferings, because we know that suffering produces perseverance;

NASB  And not only this, but we also exult in our tribulations, knowing that tribulation brings about perseverance;

ESV  More than that, we rejoice in our sufferings, knowing that suffering produces endurance,

NKJV  And not only that , but we also glory in tribulations, knowing that tribulation produces perseverance;

KJV  And not only [so], but we glory in tribulations also: knowing that tribulation worketh patience;