Yes, you can use just the parallel cables to join a companion type and a regular EU2000. You can use just the cables on two regular EU2000's but you will be limited by the 15 amp outlet on either generator. The $120 kits provide a 30 amp outlet and parallel cables so you can join 2 standard EU2000's. Before the companion was available a few years ago you had to buy the kit to parallel 2 EU2000's and get 30 amps. Also the 30 amp outlet on the companion generator is a standard L5-30R outlet so you will need an adapter for a rv style plug. Available at most camping stores and amazon.