Using this MIG consumable kit is easy. First, make sure your MDX - 100 MIG gun is turned off and unplugged. Then, replace the old tips, nozzles, and diffusers with the ones from the kit. You can choose between the .030' or .035' contact tips according to your needs. Remember to store the extra parts in the clear plastic storage box provided. As for maintenance, keep the parts clean and dry. If you notice any signs of wear or damage, replace the parts promptly. And don't forget, if you have an MDX - 250 gun, this kit won't work for you. You need to purchase 1299MDX250 instead.