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Joie Bay Latch SI 3-in-1 Harness Booster

The Joie Bay Latch SI 3-in-1 Harness Booster forward-faces up to 65 lb, is 19 in wide, and weighs 23.7 lb, per Joie. A forward-facing harness seat with rigid LATCH that converts to high-back and then backless booster, covering children up to 60 in.

  • $239.99List price
  • 65 lbHarness to
  • 120 lbBooster to
  • 23.7 lbSeat weight
See it on Joie's site

When does it expire?

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All harness-to-booster car seats

Bay Latch SI 3-in-1 Harness Booster: key facts

  • The Joie Bay Latch SI 3-in-1 Harness Booster forward-faces with a harness from 30 to 65 lb and 27 to 49 in tall; works as a booster from 40 to 120 lb and 43 to 60 in tall, per Joie.
  • Outgrown by height: "Forward-Facing: The harness straps MUST be AT or JUST ABOVE the child's shoulders. For forward-facing harnessed mode, DO NOT use the headrest higher than indicated on the label on the child restraint (headrest position 11 as indicated under the backrest softgoods)."
  • It installs with rigid LATCH or vehicle seat belt.
  • Joie says it expires 10 years after the date of manufacture.
  • Joie lists it as certified for aircraft ("Forward-facing harnessed mode: This restraint is certified for aircraft use. Booster modes: This restraint is not certified for aircraft use, as aircraft belts will not accommodate proper installation of this child restraint. (manual warnings)").
  • It's 19 in wide at the widest point and weighs 23.7 lb.

From Joie's manual and published specs. Always follow the limits on your seat's labels.

How the Bay Latch SI 3-in-1 Harness Booster stacks up

Against the 22 harness-to-booster car seats we track. The shaded band is where the middle half of them fall; the dot is this one.

Expiration10 years

Within the typical range for harness-to-booster car seats (8 years to 10 years).

This one
6 yearsmiddle 10 years10 years
Forward-facing limit65 lbHighest forward-facing limit of 22 harness-to-booster car seats

The same as most harness-to-booster car seats (65 lb).

This one
40 lbmiddle 65 lb65 lb
Width19 in5th narrowest of 11

Within the typical range for harness-to-booster car seats (18.3 in to 19.4 in).

This one
17.5 inmiddle 19 in21.9 in
Weight23.7 lb9th lightest of 15

Within the typical range for harness-to-booster car seats (16 lb to 25 lb).

This one
9.1 lbmiddle 23 lb26.2 lb
Price$239.9912th lowest price of 18

Within the typical range for harness-to-booster car seats ($79.99 to $239.99).

This one
$54.99middle $139.99$349.99

What sets the Bay Latch SI 3-in-1 Harness Booster apart

Measured against the 22 harness-to-booster car seats we compare, from each maker's published specs.

  • Weight: 23.7 lbin the middle half of the 15 harness-to-booster car seats that publish it (16 lb to 25 lb)

Next to its closest matches

Flying with the Bay Latch SI 3-in-1 Harness Booster

Joie's label: “Forward-facing harnessed mode: This restraint is certified for aircraft use. Booster modes: This restraint is not certified for aircraft use, as aircraft belts will not accommodate proper installation of this child restraint. (manual warnings)” It is 19 in wide at its widest point.

What airlines say about car seats:

  • American: “Each ticketed customer is allowed 1 stroller and 1 car seat to be checked free of charge” “If an unoccupied, adjoining seat is not available, the gate agent will check the safety seat to your final destination.” Source
  • Alaska: “We will transport your child's car seat and stroller free of charge as checked baggage.” Source
  • JetBlue: “Checking a child safety seat will not count towards your checked baggage allowance and there is no fee assessed” Source
  • Spirit: “One (1) car seat will be accepted per child as checked baggage at no charge.” Source
  • Frontier: “strollers and car seats can be checked for free.” Source
  • Allegiant: “There is no charge for checking or gate checking one car seat per fare-paying passenger.” Source
  • Breeze: “Child seats may be carried on board the aircraft if a seat has been purchased for the Infant or Child” Source

Quoted from each airline's page as of 2026-11-02.

Listed features

  • Rigid LATCH
  • Harness to 65 lb, backless booster to 120 lb
  • Ten-year life

Worth checking

  • No rear-facing mode

Where to buy the Bay Latch SI 3-in-1 Harness Booster

Prices and availability change. We may earn a commission from some links.

good to know
  • New for 2026. Some specs may not be published yet.
  • Check for recalls: Search the agency's recall list with the model number and date code from the label: NHTSA recall search.
  • Car seat use and installation: see NHTSA's car seat page, which also lists free car seat inspection by certified technicians. Check the label and the maker's instructions, and ask your pediatrician about your child.

Full specs

Joie Bay Latch SI 3-in-1 Harness Booster
TypeHarness-to-booster
List price$239.99
Forward-facing weight30–65 lb
Forward-facing height27–49 in
Booster weight40–120 lb
Booster height43–60 in
Seat weight23.7 lb
Width19 in
Head ruleForward-Facing: The harness straps MUST be AT or JUST ABOVE the child's shoulders. For forward-facing harnessed mode, DO NOT use the headrest higher than indicated on the label on the child restraint (headrest position 11 as indicated under the backrest softgoods).
Installationrigid LATCH, vehicle seat belt
Load legNo
Anti-rebound barNo
RotatesNo
Aircraft labelCertified for aircraft, per the maker
Expires after10 years

Compare the Bay Latch SI 3-in-1 Harness Booster with

How each closest rival differs from the Bay Latch SI 3-in-1 Harness Booster, from the makers' specs.

Ask the meadow

Bay Latch SI 3-in-1 Harness Booster: questions answered

From Joie's published specs, last checked 2026-11-06.

Will the Joie Bay Latch SI 3-in-1 Harness Booster fit three across or in a small car?

It's wider than 64% of the harness-to-booster seats we track, at 19 in. The narrowest is the Chicco MyFit ClearTex Harness + Booster at 17.5 in. Fit depends on your vehicle; check each seat's manual and your vehicle manual. Car seat use and installation: see NHTSA's car seat page, which also lists free car seat inspection by certified technicians. Check the label and the maker's instructions, and ask your pediatrician about your child.

Can you bring the Joie Bay Latch SI 3-in-1 Harness Booster on a plane?

Yes, Joie lists it as certified for aircraft; look for the red-lettered label that says so. The FAA asks that a car seat go in a window seat so it doesn't block the aisle, and the crew will look for that label. It weighs 23.7 lb to carry through the airport.

Bay Latch SI 3-in-1 Harness Booster or Grow with You Harness-to-Booster: what's different?

By the makers' specs, the Grow with You Harness-to-Booster has no added flame retardants (maker's claim). See every spec side by side.

Is it OK to buy a used Bay Latch SI 3-in-1 Harness Booster?

NHTSA publishes guidance on used car seats on its car seat page. Joie lists a lifespan of 10 years from manufacture for this model. Check the label and the maker's instructions, and ask your pediatrician about your child.

Still wondering? Write to us at hello@cribpicks.com and we'll look it up.

More harness-to-booster car seats

Where these specs come from

Last checked 2026-11-06. Spot something wrong? Tell us. Read our editorial and safety policy and corrections.