The calves are the most notable, but his upper arms don't look quite right either to me.
You can't see lumps in his arms because he didn't put enough in them to make them lump out. Only the guys that are dumb and/or desperate shoot too much too fast and that's one reason why it becomes lumpy. Dexter shot it slowly.
In his arms, the telltale sign are the injection marks near his armpit area on both arms- both bi's and tri's.
