Extensions increase ripple. And increased ripple increases system instability, especially when OC'ing.
So, better to buy full CableMod set that replaces all your PSU's power cables (like i've done with all 3x of my builds, specs and pics in my sig), rather than buying extensions.
This is NOT CableMod product. Instead looks like some cheap knock-off. AsiaHorse brand, that i have never heard of. Can melt and kill your hardware. So, better buy reputable brand.
CableMod RT-series cables are compatible with your PSU,
lineup:
https://cablemod.com/products/?orderby=date&filter_series=rt-series&show_products=90
Or use custom configurator to make your own length/color cable,
link:
https://store.cablemod.com/configurator/
Here's the diff between ModMesh and ModFlex cables,
article:
https://cablemod.com/?faqs=what-is-the-difference-between-modmesh-and-modflex
The CableMod cables i have (all 3x different color sets) are all ModFlex.