The shape of this Stairway
What handicap the user has on the selection of narrow stair lift. If you cannot stand or walk, then a chair stair lift would be the best option, while some might need a standing stair lift to conserve space. There are a number of manufacturers offering both features to permit users to pick. They may be a costly product to buy and users should report that which is best suited to your own requirements.
Reconditioned Narrow Stair Lift