As far as I know, the main difference between the two rods are the eyes. Baitcastng Rods have smaller eyes that are facing upwards. Spincasting Rods have larger eyes that get smaller as they go towards the end. I don't know if the rods are made up differently internaly, maybe someone else can answer that. I do mix and match the rod and reels somtimes. I have a spincasting rod with a baitcasting reels on it for my trout fishing, and it works great.