Why i can't change the "explosion" value?

Hi, my script don't work, it said

DestroyJointPercent is not a valid member of Part

My script is

script.Parent.ChildRemoved:connect(function(hit)
	a = Instance.new("Explosion")
	a.DestroyJointRadiusPercent = script.Parent.DestroyJointPercent.Value
	a.BlastPressure = script.Parent.BlastPressure.Value
	a.BlastRadius = script.Parent.BlastRadius.Value
	a.Position = script.Parent.Position
	a.Parent = workspace
	script.Parent.Parent:Destroy()
end)

Can someone help?