I made some beam that's supposed to tween out from one side but it tweens from both sides. This is what happens: https://gyazo.com/f1b4656c69b7e74de778cf328971a8dd
you are only changing the size of the part on the tween. You also need to tween the position to match the new beam size you are tweening. Usually you need to tween the position to half of the size you increased. Example: you increased your beam size by 10 studs, so increase the beampos to the same direction by 5 studs (10/2).