Unless things have changed in the last few years, the Alko side lift does not fit into the same fixing as the scissor jack (mainly because the scissor jack does not have such fittings) I've had both and the side lift jack is far easier to use, but as john says, leave the car connected while you use it. For the price and the weight, a small bottle jack (eg from screwfix or Motorway) is well worth carrying, as if you get unlucky, you will find the side of the caravan with the punctured wheel is too low for either type of jack (but do leave the car connected, all brakes on and don't get too far underneath). Also, from bitter experience, keep any locks on the underslung spare wheel free from dirt and well oiled, so that you can get at it easily on a cold wet dark night.