Forge ones are made from flourosilicone which is oil resistant and heat resistant... normal silicone can be used in some circumstances though, I use a 60mm to 51mm reducer on my GT30 but I still have the K04 heat jacket wrapped around it... on top mount big turbo conversions its a non issue as the silicon is much further away from the manifold heat source...
If you need a replacement hose then the Forge one is the best option... better and cheaper than the OEM one... its designed to fit properly as its a different angle/shape to the normal 90 deg elbows...
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