The REELEX I (1st generation) is more compact compared to REELEX II making the first generation more space efficient. Also, the coiled cable is inserted through the side of the box (1st photo). The REELEX II comes in a bulky box and larger compared to the REELEX I. The bulky box helps prevent damage to the coil which may cause tangles due to transport of the cable. The REELEX II is inserted through the front where the Payout hole is located (2nd & 3rd photo).