Santi BZ420X Heated Undersuit - Made to Measure
Dispatched in 8 to 10 weeks
The Santi BZ420X Heated Undersuit is an advanced version of Santi’s flagship model, designed for even greater warmth and comfort while diving in a drysuit. It offers unparalleled thermal comfort even in extreme conditions thanks to construction improvements and new materials.
Gender
Santi BZ420X Heated Undersuit - Made-to-measure
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 cuts.
Note: Batteries and connectors are not included and must be purchased separately. Never exceed 12V when operating this heating system.
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.

HOW TO MEASURE YOURSELF FOR SANTI SUITS
Carefully watch SANTI's "Instructions for Self-measuring" video below. The video shows all measurements for Made-to-Measure suits.
STEP-BY-STEP
Download the Santi MADE TO MEASURE FORM. Use only a taylor's tape measure that has a centimeter scale (only use metric with cm).
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.
HEAD - approximately 1cm above the eyebrows to choose the correct hood size.
NECK - above the t-shirt line, under the Adam’s apple and the end of the neck.
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.
SHOULDER TO SHOULDER - back shoulders length from one top arm bone to another.
OUTER ARM LENGHT - from the back neck spine bone to the wrist while the arm is fully stretched.
INSIDE ARM LENGHT - from armpit to wrist.
LADIES ONLY / SIDE TRUNK LENGHT - from the armpit to the waist line.
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.
WRIST - between the palm and the wrist bone.
CHEST - first measure the chest in rest and then after breathing in air. Normally the difference should be around 3-5cm. For ladies measure in the fullest point of the bust, preferably while wearing a bra.
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.
LADIES ONLY / BACK HEIGHT - centrally from the neck spine bone to the waist line marked with the belt.
LADIES ONLY / CHEST HEIGHT - from the soft neck area (where the neck ends) to the bust line in the fullest point.
HIPS - in the fullest point of the buttocks.
THIGH - widest point approximately 5cm from the crotch area.
CROTCH TO KNEE - from crotch to knee.
CROTCH TO FLOOR - hold one end of the measurement tape in a convenient place in the crotch and measure to the heel end.
CALF 1 - measure the calf in the widest point.
CALF 2 - height from the widest point of the calf to the floor.
CALF 3 - measure the calf 20cm from the floor.
ANKLE - measure the ankle on the ankle bone.
FOOT - place the tape on the floor and step on it to measure from end of heal to end of toes.
UNDERWATER EXPLORERS LTD/DIRDIRECT DISCLAIMER:
It is the customers responsibility to choose a correct size. Made to measure 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 a made to measure suits unless measured by us.
SHIPPING:
We aim to dispatch all in-stock items within 2 working days but 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.
Please refer to our Shipping Policy and Returns & Refunds Policy for detailed information on delivery terms and returns.
Our current shipping rates are as follows:
- UK mainland orders £50 and over: FREE - DPD or alternative courier delivery*
- UK mainland orders under £50: £5.50 Fixed Rate - DPD or alternative courier delivery*
- Scotland Highland (inc. AB31+ Post Codes), Scottish Islands & Isle of Man: £11.00 Fixed Rate
- Channel Islands & Northern Ireland: £16.00 Fixed Rate
- European Union: £15.70 + 6% of order value (maximum £35)
- Rest of the World: £22.00 + 9% of order value (maximum £65)
- BFPO Post Codes: £23.00 (see Delivery Terms for BFPO at end of this page)
- FPO & APO Unfortunately, we are unable to arrange delivery to FPO/APO addresses
- PO Boxes - All our PO Box deliveries need to be signed for, therefore, unless prior arrangements are made with us, we do not deliver to PO Boxes.
*The dispatch days listed in our product listings refer to working days, excluding weekends and UK holidays. Products that need to be ordered from the manufacturer or distributor's stock, are temporarily out of stock, are subject to backorders, or are marked as Special Orders may take longer to dispatch. We will notify you of this once your order is confirmed.
INTERNATIONAL EXCEPTIONS:
For international orders containing weights, cylinders (excluding suit inflation bottles), and Suex scooters, please contact us in advance before placing your order.
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. We will let you know the cost before processing any order.
All cylinders we ship within and outside of UK mainland are filled and tested on site before being emptied for dispatch. Cylinders shipped outside of the UK will be empty and will also have their valves removed, requiring reassembly after you receive delivery. Twinset manifolds and bands will also be removed and dispatched together with the cylinders for safe global shipping.
RETURNS & REFUNDS
We offer a 30 day return for any product sold under our Returns & Refunds Policy Please contact us before any return with your order number and date details. Receive our Returns Authorisation Form and instructions and enclose them with your return to expedite a refund. Detailed information is available in our Returns & Refunds Policy.
Email us at sales@dirdirect.com or call us on +44(0)1305 824 555
Note that all returned items are shipped at the customer's own risk and remain the customer's property until received by Underwater Explorers, so please ensure they are packaged well and use reliable postal services with tracking facilities. The goods will be inspected on arrival.
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 £45 and above) the UK shipping rate may be deducted from any UK mainland refund unless linked to a fault/defect claim.
Please contact us with your order number and name before sending any returns to:
Underwater Explorers – Returns
Unit 1, Maritime Business Centre
Mereside, Portland
Dorset, DT5 1FD
United Kingdom
Please refer to our Shipping Policy and Returns & Refunds Policy for detailed information.































