How to use the flex tool?
Here's the Tutorial.
Make a box.
Now you have the part for flex.
Under flex choose bending and input body choose the box.
Change the angle value to 50 degrees. We don't need to adjust the planes because they are automatically adjusted.
Click OK. Now you can see the flexed body.
Edit the Flex1 feature.
Change the flex type to twisting. Keep the same angle value and click OK.
You can see the twisted body.
Again edit the feature and choose tapering type and taper factor be 1/2 or 0.5.
Now you have a tapered body.
Again edit the Flex1 feature. And this time choose Stretching. Choose stretch distance value to be 40. Click OK.
You have a stretched body. Any hole if present in the body will also be stretched.