O'Neill Psycho I 4/3 Back Zip Wetsuit

O'Neill Psycho I 4/3 Back Zip Wetsuit 4.5 5 2
SKU: ONL4394
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The O'Neill Psycho I ZEN Zip Wetsuit is a team inspired high performance wetsuit. Built with ultra gooey TechnoButter 2 Neoprene and ultra-minimal seam styling the Psycho I has insane flexibility, fit and warmth. The ZEN Zip back entry minimizes water entry along the zipper and makes getting in and out of your suit a snap. Offering unrestricted mobility, enhanced durability and incredible fit, this suit is a favorite for the competitive surfer. The Psycho I will raise your performance level to new heights.


Thickness: 4/3mm

Neoprene: TB2 Neoprene

Seams: Single Fluid Seam Weld

Zipper: Back Zip

Hood: None

Model Year: 2015/2016

Manufactures Part Number: 4394


Product Features

  • Technobutter 2 Neoprene: Advanced super stretch neoprene, 20% lighter, 30% less water absorption with improved durability and quick dry properties
  • Single Fluid Seam Weld: Watertight Stitchless Technology that keeps water from entering at all seams and critical points
  • Double Super Seal Neck: A toasty warm two-layer design featuring a 360 smooth skin interior lining, wide adjustability and a secure lock down.
  • Z.E.N. Zip Closure System: Pullover internal seal that blocks out water for maximum warmth. Water that penetrates the Z.E.N. Collar or Short Zip is blocked by the Barrier-2 and forced out the Drain Hole.
  • Super Seal Cuffs: Fused to create a very low profile at the cuff ending creating the best seal ever. The low profile prevents water entry and improves durability in your wrist and ankles.
  • Super Minimal Seam Design: Minimal seam design for greater flexibility and mobility.
  • Krypto Knee Padz: Abrasion resistant, high stretch neoprene panel with ergonomic shaping designed to extend the life of the wetsuit and protect the knee while punching through waves.
  • External Key Pocket: Located along the lower leg inseam, this key pocket is easy to access and completely secure.
  • Plasma Wrist and Ankle Seals: Helps prevent flushing through the wrists and ankles and keeps a secure fit.
  • Contortionist Seamless Shoulders: Seamless shoulder panels for unrestricted mobility and ultimate stretch.
  • Strategic Seamless Paddle Zones: An ergonomic, seamless undersleeve panel that allows for unrestricted motion and eliminates rashing.


O'Neill Psycho I 4/3 Back Zip Wetsuit Soooper flexibleReview by Fonterello Fonterello
This suit is really flexible with the technobutter neoprene. No binding or bunching at all. I finally got to try this suit in 40deg water. Really flexible in the arms for swimmers.
I ordered the mutant at first. Tried it on. The top entry is not easy for an older less flexible guy, and would be extremely difficult to dawn if you didn't have help. So I returned it to cleanline, no problems at all.
Then I ordered the psycho 1 with the back zip. I kited for almost 2 hrs in cold water, then when I got out, someone had borrowed my car and I had to wait with my suit on for 45 mins, and I was just fine. It still kept me warm and comfy. I would recommend to a friend no problem. The neck seal doesn't seem that tight, but I took a few dunks in the water and never had any body flush or any water enter at all. So I guess it's okay. Overall it seems like a good suit.
Thanks cleanliness for your great service.
(Posted on 4/12/2015) 2015-04-12
O'Neill Psycho I 4/3 Back Zip Wetsuit Light-weight, comfy and warmReview by Geoff Geoff
This wet-suit is very light compared to other 4/3 suits, but still provides the warmth! This kept me from getting hypothermia during World's Toughest Mudder 2014 during a overnight sandstorm at Lake Las Vegas. The lightweight and stretchy technobutter allowed un-hindered movement during running, swimming, climbing, jumping, etc. It is also easy to get in and out of (by yourself). Knee pads held up well even after crawling through mud and rocks.
(Posted on 12/3/2014) 2014-12-03

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Size Chart

The staff at Cleanline Surf specialize in sizing O'Neill Wetsuits. If you have never tried an O'Neill suit before, we strongly urge you to call us for expert advice on sizing. We do have a size chart available below, but please take it with a grain of salt. For the perfect fit the first time please call and speak with one of our wetsuit experts.

2XS5′6″-5′8″115-130 lbs32.5-34.5″27-29″
XS5′7″-5′9″125-140 lbs34.5-36.5″28-30″
S5′8″-5′10″135-155 lbs36.5-38.5″29-31″
ST6′0″-6′2″145-165 lbs36.5-38.5″29-31″
M5′9″-5′11″150-170 lbs38.5-40.5″30.5-32.5″
MS5′6.5″-5′8.5″140-160 lbs38.5-40.5″30.5-32.5″
MT6′1″-6′3″160-180 lbs38.5-40.5″30.5-32.5″
L5′10″-6′0″170-190 lbs40.5-42.5″32.5-34.5″
LS5′7.5″-5′9.5″160-180 lbs40.5-42.5″32.5-34.5″
LT6′2″-6′4″180-200 lbs40.5-42.5″32.5-34.5″
XL5′11′-6′1″190-210 lbs42.5-44.5″34.5-36.5″
XLS5′8.5″-5′10.5″180-200 lbs42.5-44.5″34.5-36.5″
XLT6′3″-6′5″200-220 lbs42.5-44.5″34.5-36.5″
2XL6′0″-6′2″210-230 lbs44.5-46.5″36.5-38.5″
3XL6′0″-6′2″230-250 lbs47.5-49.5″38.5-43.5″

Full O’Neill Wetsuit Sizing Chart



If the product is found to be defective under normal use and proper care, O'Neill will repair or replace the product at our sole discretion. The decision to replace or repair a product is made by the O'Neill Warranty Department after receipt of the defective product. At no time does the O'Neill offer refunds. Defective product should be returned clean and dry, postage prepaid. Please include a note with product description, product defects, requested action, return address (be sure to include postal code, especially for Canadian addresses), daytime phone number with area code, customers name and a copy of the purchase receipt sent to the address below.

Suits without a copy of the purchase receipt will NOT BE COVERED UNDER WARRANTY.


  • Products classified as seconds
  • Fading from sunlight
  • Alterations
  • Materials over 1 year (from date of original purchase), or 90 days for accessories
  • Repairs or alterations done by anyone other than O'Neill or an O'Neill authorized repair facility
  • Warranty request without original receipt


Flat-Stitched Products, Glued and Blindstitched Products, and Fluid Seam Weld Products

  • Limited 1-year warranty (from date of original purchase) on workmanship and materials.

Neoprene Dry Suits

  • Limited 1-year warranty (from date of original purchase) on workman ship and materials (waterproof zipper excluded)


  • Limited 90-day (from date of original purchase) warranty on workmanship and materials


For repairs received from the dealer or end user, O'Neill offers:

  • 10 Business Day Turnaround for warranty Stitched Suits
  • 10 Business Day Turnaround for warranty Glued Suits
  • 20 Business Day Turnaround for warranty Fluid Seam Welded Suits
  • 30 Business Day Turnaround for all Non-Warranty Repairs

Repairs are to be returned clean and dry, postage paid. Please include the name and a daytime phone number with area code, return address, product description, and requested action.

Send Repairs To:

O'Neill U.S. Warranty Repair
1022 Bay Marina Drive, Suite 140B
National City, CA 91950
Tel: 1-800-331-1637


Returns are easy! We understand that in some situations returns or exchanges may be necessary. We also want you to be stoked on your purchase. If you are not 100% satisfied with your purchase you may return it for a full refund, or exchange within 30 days of receiving your order. Items must be in new condition with original tags and packaging.

Click here for our full Return Policy