Why is this brick not resizing properly through a script?

b.Size = Vector3.new(15.4,27.4,0.2) This is resizing it, but the Z value is resizing to "1" not 0.2. Can someone help me fix this?

Note: Didn't want to choose a tag, but I had to, I know this isn't exactly Cframing, but it's close.

Parts require the FormFactor to be "Custom" in order to resize to non-bricky increments.

b.FormFactor = "Custom" before setting the size should make it work.