Length, weight and material build of a fly rod all matter. The size of the fly rod determines the size of the fish. The material build determines the flexibility. The fly rod weight doesn’t mean it weighs that much but rather it’s a rating to combine it with a fly reel and fly line. The fly rod action in simple term describes the flexibility of the fly rod on the back-cast. More expensive fly rods doesn’t necessarily make them better, especially not for a beginner. If you don’t know the equipment you’re purchasing, you will waste money by purchasing incompatible fly rod, fly reel and fly line combination. Or you’ll simply purchase the wrong combination for the fish you’re fishing for.