Front Sight Swap Question

[Callirye]

I want to swap my current front sights (came on my m15a4 carbine) to a foldable one which I found, as I am getting a red dot. However, at the moment my hand guard 'holding thing' appears to be attached to the old sight for support.

I was wondering if all sights have this 'holding' function or if I will need to buy something else to accommodate for it.

Thanks,

Callirye.