Britax Millenia vs B-First iFix: What’s the Difference?

Parents prioritize their child’s safety and comfort during car rides, and Britax offers a selection of high-quality car seats to meet various family needs.

In this article, we’ll compare the Britax Millenia and B-First iFix car seat models, focusing on their differences to help you determine the best option for your family.

Important note: This article is solely intended to provide a comparison of the features of these Britax car seats. It is not intended to be taken as advice or guidance on which car seat to choose. We recommend that you visit the Child Car Seats website to evaluate car seat safety and consult a professional installer for advice on installation. We also encourage you to consult the manufacturer for specific queries.

Size and Weight

The Millenia car seat weighs 8.9 kg, while the B-First iFix is slightly heavier at 9.9 kg. The B-First iFix also has larger dimensions in both forward and rearward-facing positions. If you prefer a lighter car seat or need to save space in your vehicle, the Millenia may be more suitable.

Convertibility and Installation Method

Both car seats cater to children aged 0-4 years and offer rearward and forward-facing configurations. They support seatbelt and ISOFIX installations, with top tethers for added security.

However, the B-First iFix is not aircraft-compatible, unlike the Millenia model. If traveling by air with your child’s car seat is a priority, the Millenia would be the better choice.

RELATED: Britax Graphene vs B-First iFix

Side Impact Protection

While the Millenia car seat has EPS foam protection for side-impact safety, it lacks the advanced deployable Side Impact Cushion Technology (SICT) found in the B-First iFix model. The B-First iFix offers both torso and head protection with its advanced deployable SICT.

Britax states that “Advanced SICT is a deployable safety innovation with crumple zone technology. Located on the Headrest and Torso, the unique design combines advanced safety and freedom of space.” – Source

Hardware Product Features

Although both car seats share several hardware features, such as rebound bars, hassle-free harness systems, and adjustable headrests, there are notable differences:

  • Rebound Bar: The B-First iFix comes with a rebound bar cover, while the Millenia does not.
  • Rear Facing Level Indicator: The B-First iFix has a rear-facing level indicator, while the Millenia does not. This feature helps ensure the correct installation angle for rearward-facing positions.
  • Seat Belt Lock-offs: The Millenia has seat belt lock-offs for both rearward and forward-facing positions, while the B-First iFix does not.
  • Frontal Easy Adjust Headrest: The B-First iFix comes with a frontal easy adjust headrest for added convenience, which is not available in the Millenia model.
  • Forward Facing Recline Positions: Both car seats provide four forward-facing recline positions, offering flexibility and comfort for your child.


Both car seats feature Thermo 5 performance fabric, EZ Buckle crotch pads, and shoulder pads for improved comfort. However, the B-First iFix offers additional comfort features:

  • Hardware Ventilation: The B-First iFix has hardware ventilation, ensuring better airflow and increased comfort for your child.
  • Comfort / Newborn Insert: The B-First iFix comes with removable wings in its newborn insert, providing extra support for smaller babies.
  • Vehicle Seat Protector: Both the Millenia and B-First iFix include a vehicle seat protector.


The Millenia car seat has a storage pocket for added convenience, while the B-First iFix does not. If storage space for small items is important to you, the Millenia model may be a better fit.


When comparing the Britax Millenia and B-First iFix car seats, consider your preferences regarding size, weight, safety features, and additional comfort options.

While the Millenia is lighter and offers better storage, the B-First iFix provides advanced side-impact protection and enhanced comfort features. Assess your family’s specific needs to choose the most suitable car seat for your child.