Santi BZ420X Heated Undersuit
Dispatched in 6 to 10 weeks
The Santi BZ420X Heated Undersuit is an advanced version of Santi’s flagship model, designed for even greater warmth. It offers unparalleled thermal comfort even in extreme conditions thanks to construction improvements and new materials.
Gender
Santi BZ420X Heated Undersuit
The Santi BZ420X Heated Undersuit represents an advanced evolution of Santi’s flagship model for drysuit diving. It provides unparalleled thermal comfort, even in extreme conditions, thanks to significant construction improvements.
This heated undersuit protects the entire body by evenly warming the trunk, thighs, and arms. For the best results, you should wear it over a thin base layer to transfer heat directly to your skin. Consequently, you remain warm and comfortable underwater even if your battery power becomes low or completely drained.
Innovative Features and Design
Santi includes several upgrades in this version, such as a thicker inner layer for superior thermal insulation. This makes the BZ420X Heated significantly warmer than the previous BZ400 Extreme model.
Furthermore, the new cable layout ensures more efficient heating and much better heat distribution across the body. The improved "brick" quilting pattern enhances flexibility while providing a more ergonomic fit. Additionally, the smooth inner material allows you to don and doff the suit with much greater ease.
System Requirements and Safety
To power the internal heating wires, use the Santi Drysuit Connector or Thermovalve 303. Santi offers three battery options: Battery 9Ah, Blue Power 14Ah and Blue Power 28Ah.
For the best results, wear a Santi heated undersuit over a thin thermal underlayer to direct heat toward your body safely. Additionally, a built-in safety switch prevents overheating and ensures a steady current flow.
Santi BZ420X Heated Undersuit Highlights
- Maximum heating temperature of 45°C with 110W of power.
- Heating elements positioned strategically on the torso, thighs, and arms.
- Thick inner layer (290g/m2) and robust outer layer (420g/m2).
- Offers approximately 3 hours of run time on a 28Ah battery.
- Includes integrated cables in the sleeves for easy heated glove connection.
- Features P-valve holes on both sides and water-resistant cuffs as standard.
- Ergonomic wiring allows for unrestricted movement and a natural body fit.
- Available in men's and women's sizes or a made-to-measure option.
Note: Batteries and connectors are not included and must be purchased separately. Never exceed 12V when operating this heating system.
FREE "Made to Fit" service
Very few divers require a totally made to measure suit due to the wide range of standard sizes available from Santi Diving. With this in mind, Santi offers a free of charge Made-to-Fit service to any standard Santi BZ420X Heated Undersuit ordered, sculpting standard suits to a divers' measurements.
With your Santi BZ420X Heated Undersuit order, you can request up to 4 changes (ranging from 2 to 5 cm) to any of the standard size measurements listed under chest, inner arm, biceps, forearm, waist, hips, inner leg, thigh, calf or body trunk on the Santi size chart.
If you would require more than 4 changes to make your suit perfect, you can add two more changes for a small additional charge.
Santi Heating Systems at glance
The Santi Heated BZ420X Undersuit has been designed as part of the Santi heating system, which currently includes items such as the Santi Heated Flex 2.0 Undersuit, Heated Vest Flex 2.0 and Heated Gloves.
Want to know which batteries can be used with Santi heating systems and decide which suits you best? Check out our Comprehensive Review of Batteries for SANTI Heating.
Read our SANTI Thermovalve and Drysuit Connector comparison.

FREE "Made to Fit"
Very few divers require a totally made to measure suit due to the wide range of standard sizes available from Santi Diving. With this in mind, Santi offers a free of charge Made-to-Fit service to any standard size suit ordered, sculpting standard suits to a divers' measurements.
With your order, you can request up to 4 changes (ranging from 2 to 5 cm) to any of the standard size measurements listed under chest, inner arm, biceps, forearm, waist, hips, inner leg, thigh, calf or body trunk on the SANTI size chart.


UNDERWATER EXPLORERS LTD/DIRDIRECT DISCLAIMER:
It is the customers responsibility to choose a correct drysuit size. Modified undersuit returns are not accepted under any circumstance unless Underwater Explorers Ltd/DirDirect has made a mistake. We do not take any responsibility for a fit of suits unless measured by us.
HOW TO MEASURE YOURSELF FOR SANTI SUITS
Carefully watch SANTI's Instructions for Measuring video below. The video shows all measurements for made to measure suits. For standard size or Made-to-Fit measurements please use the Size Chart.
STEP-BY-STEP
Never take your own measurements yourself! Measurements should be taken by another person to make sure all measurements are taken tight up to the body and at correct placement for a specific measurement.
It is important that you stand straight, look forward and do not bend over while you are being measured. It is equally important to take the measurements only while wearing thin clothing, close to the body. Don’t leave any additional measurement allowance.
CHEST - on the widest point.
INNER ARM - from armpit to wrist.
BICEPS - widest point on the loose arm. If you have a visibly athletic figure it is advised to measure the biceps also with bent elbow.
FOREARM - in the widest point.
WAIST - measure on the belly button level. Remember to measure the waist line in the widest point on the belly button line. To measure a female waistline correctly, use any kind of "marker belt" and fasten it around the waist line.
HIPS - in the fullest point of the buttocks.
INNER LEG - hold one end of the measurement tape in the crotch and measure to the heel end.
THIGH - widest point approximately 5cm from the crotch area.
CALF - measure the calf at the widest point.
BODY TRUNK - hold one end of the tape on the central point of the neck end and lead the tape across the crotch to the back. Mark the place where tape ends and measure the rest of the line to the spine neck bone. Make sure the tape is close to the body including all the curves.
UNDERWATER EXPLORERS LTD/DIRDIRECT DISCLAIMER:
It is the customers responsibility to choose a correct drysuit size. Modified undersuit returns are not accepted under any circumstance unless Underwater Explorers Ltd/DirDirect has made a mistake. We do not take any responsibility for a fit of suits unless measured by us.
SHIPPING & RATES
You can find our current shipping rates in our Shipping Policy & Rates.
We aim to dispatch all in-stock items within 2 working days. The Dispatch Days listed in our product listings refer to working days.
We will inform you of approximate delivery times should any item on your order be out of stock or on supplier backorder due to current manufacturing or transport delays caused by global shortages and/or impeded production.
INTERNATIONAL EXCEPTIONS
Please contact us in advance for a shipping quote before placing an international order for weights, cylinders (excluding suit inflation bottles), and Suex scooters. These products are not included in our global max-capped shipping rates.
They are only shipped outside the UK mainland after the freight cost is calculated based on the parcel's total weight, dimensions, delivery location, and the courier service used.
RETURNS & REFUNDS
We offer a 30-day return for any product sold under our Returns & Refunds Policy.
Please email us at sales@dirdirect.com with your order number to receive our Returns Authorisation Form and instructions.
Return postages are at your own cost and our outbound shipping costs (if items are sold with integrated basic shipping charges i.e. Free shipping for orders above certain amount) the current UK shipping rate will be deducted from any UK mainland refund unless linked to a fault/defect claim.































