Let’s learn the difference between Shark Rocket Pro Cordless Stick Vacuum IZ140, IZ140C, IZ142 and UZ145 below:

images from shark clean.com

• Headlights
  The IZ140 and IZ140C have no headlights whereas the IZ142 and UZ145 equipped with LED headlights on the nozzle.
• Accessories
  The IZ140 comes with a MultiFLEX Wand, a Dusting Brush and an 8-inch Crevice Tool.

  The IZ140C comes with a Straight Wand, an Upholstery Tool and an 8-inch Crevice Tool.

  The IZ142 may come with a Straight Wand or a MultiFLEX Wand, a Pet Multi-Tool and an 8-inch Crevice Tool.

  The UZ145 may come with a Straight Wand or MultiFLEX Wand, a Dusting Brush and an 8-inch Crevice Tool.

• Color
  The IZ140 is Teal, the IZ140C is Green, whereas the IZ142 and UZ145 are Orange.

Similarities:

• Can be used as a stick vacuum or transformed into a handheld vacuum to tackle different cleaning jobs.
• Cordless, powered by 1900mAh 21.6V Lithium-ion rechargeable battery (battery part number XFBT620). Battery can only be charged in the vacuum.
• Self-cleaning brushroll for removing hair without hair wrap.
• PowerFins provide non stop contact to clean carpets and floors.
• Carry 5-year limited warranty on the unit, 2-year limited warranty on the battery.
• Washable filters. It is recommended to rinse them with water only, clean the 2 pre-motor filters at least once a month and post-motor filter at least once a year.
• Bagless, transparent dust cup holds 0.34 dry quarts.

Some questions and answers:

• Do they have a wall mount?
  No.
• Is the battery removable?
  The battery is fixed, it is replaceable but requires tools to replace. Not the type that you can get a second battery to easliy swap out to extend the running time.
• How long will it take to charge?
  A full charge takes approximately 3 – 3.5 hours.
• What’s the run time?
  Depends on which mode and setting you choose.
  They have Standard mode and Boost mode, Bare Floor setting and Carpet setting.
  When using as a hand vac, they run up to 40 minutes in Standard mode, up to 10 minutes in Boost mode.
  While using with the floor nozzle, choosing Bare Floor setting, they run up to 25 minutes in Standard mode, up to 10 minutes in Boost mode.
  While using with floor nozzle, choosing Carpet setting, they run up to 20 minutes in Standard mode, up to 10 minutes in Boost mode.
• Do you have to continuously hold a button to use them?
  They have On/Off control, in standard mode, you do not have to keep pressing the button. However, if you need more suction power, you will need to pull the Trigger
  on the handheld vacuum to enter the Boost mode for extra power. And release it to return to standard mode.

The Shark HZ2002 and HZ251 corded stick vacuum cleaners look similar. If you are deciding between them, we will help you make an informed purchase.
Below is the main difference between Shark HZ2002 Vertex Ultralight DuoClean PowerFins Corded Stick Vacuum and Shark HZ251 UltraLight Corded Stick Vacuum:

images from shark clean.com

• Floor Nozzle
  The HZ2002 has a DuoClean PowerFins floor nozzle with self cleaning brushroll whereas the HZ251 has a one roller floor nozzle with self cleaning feature.
  The DuoClean PowerFins floor nozzle has two rollers: a soft roller to pull in large particles and fine dust for a polished look on hard floors, and a roller with flexible silicone fins to deliver non stop contact on carpets and floors, result in more dirt collection in every pass.
  Shark claimed that the self-cleaning brushroll will pick up hair without wrapping problems.
• Cord Length
  The HZ2002 has a cord length of 30-foot whereas the HZ251 has a 25-foot cord.
• Control
  The HZ2002 has a floor selector button that allows you to press to toggle between Bare Floor and Carpet settings. Whereas the HZ251 uses a slider to get things done.
• LED User Interface
  The HZ2002 has LED Display that makes it intuitive when changing cleaning modes. While the HZ251 does not has the LED display.
• Accessories
  HZ251 comes with a Pet Crevice Tool, Upholstery Tool, and an Anti-Allergen Dusting Brush, Onboard Storage Clip.
  HZ2002 comes with a Dusting Brush, Crevice Tool, Self-cleaning Pet Power Brush, Onboard Storage Clip.

  Pet Crevice Tool is a 8-inch tool designed for removing pet hair from corners, baseboard, and other hard-to-reach spaces.

  Upholstery Tool can be used to remove pet hair, dust, and large debris from delicate upholstered fabrics.

  Anti-Allergen Dusting Brush has nylon fiber bristles designed for removing cleaning the most delicate surfaces.

  Dusting Brush dusts and cleans delicate surfaces such as lampshades.

  Crevice Tool is for cleaning in tight places and hard-to-reach areas.

  Self-cleaning Pet Power Brush actively removes hair wrap as it cleans upholstery and carpeted surfaces.

  Onboard Storage Clip can be snapped onto the wand to store up to two accessories.

• Weight
  The HZ2002 weighs 9.05 lbs versus 8.31 lbs on the HZ251.
• Cleaning Path Width
  The HZ2002 has a cleaning path width of 8.11-inch versus 8.71-inch on the HZ251.

Similarities:

• Corded.
• 2-in-1 design: can be used as a handheld or a stick vacuum.
• Featured self-cleaning brushroll.
• Bagless, have a dust cup holds up to 0.32 dry quarts.
• Both have two floor settings.
• Have washable foam and felt filters.
• Removable dust cup for emptying.
• Hand unit can be hooked onto the wand for storage.
• Carry 5-year limited warranty.

Questions and answers:

• Do they have On/Off control or do you have to keep pressing the trigger?
  They have On/Off power button. You don’t have to keep holding down the button.
• Do they stand upright by their own?
  No. When not in use it will need to be leaned against something or the hand unit need to be stored on the hook on the wand.
• Do they have headlights?
  Yes, there are headlights on the nozzle. But no lights on the hand unit.
• Do they have HEAP filter?
  No.
• Are the filters washable?
  Yes.
• Do they have a wall mount?
  No.
• Can the rollers be turned off when cleaning delicate surfaces?
  No. In Bare Floor setting, the roller still spins, but at a slow speed.