The instructor on my first technical course loftily informed me that I would be using what he considered to be the finest regs available for technical diving, Apeks, and not the hugely second-rate non-Apeks stuff with which I had arrived. He didn’t actually say that second bit out loud, of course, but it was obvious what he was thinking.
As it turned out, the Apeks regs I used were grand performers and I’d have been quite happy to have owned them, although in all honesty I didn’t think they were any better than my own regs, but then I’m not a test machine, and assessing work of breathing is notoriously difficult without one.
With a reputation like that, the weight of expectation heaped on any new product is enormous, and the brand-spanking-new XL4 has a lot to live up to.
Apeks is not being shy about it, and describes its new regulator as being ideal for cold- or warmwater use, as well as perfect for technical divers intent on keeping the weight of their kit down. That covers pretty much all the bases, as far as I can see.
Apeks sent me its XL4 in Stage 3 kit form for review. This consists of the XL4 DIN fitting first stage plus an XL4 second stage in black and an octopus XL4 second stage in yellow.
You can buy the XL4 with a single second stage or as a Stage 4 kit, which also includes a contents gauge. An A-clamp/yoke fitting version is available.
Opening the box revealed a very nicely made piece of kit, with the Apeks name clearly visible on every available surface to ensure that you have immediate bragging rights and dive-site credibility.

The Design
The first stage is based on the well-respected DS4.
It is, of course, environmentally sealed and has had a lot of thought put into maximising the surface area available for heat exchange to prevent icing, consequently avoiding those exciting freeflows that can make inland UK diving so much fun in the winter.
An over-moulded end-cap also helps to prevent freeflows, and adds some protection against impact damage for your beautiful new valve set.
An over-balanced diaphragm design allows the intermediate pressure in the hose between first and second stages to increase more quickly than ambient pressure on descent, and is claimed to improve performance at depth.
The first stage has four medium-pressure ports and a single high-pressure port for a contents gauge or sender to mate with your gas-integrated computer.
You might like to know that the first stage isn’t much larger than a gas-pressure sender unit. In fact, the whole kit and caboodle is neat and small and just yummy.
The new XL4 second stage is compact and lightweight to prevent jaw fatigue on long dives, and comes complete with the legendary Comfobite mouthpiece.
This features a bridge across the upper palate intended to make it easier to hold the second stage in your mouth without having to bite down on it.
Actually, Comfobite mouthpieces might not be legendary, but they ought to be. I’ve always used them, regardless of the make of reg I’ve used, and they work extremely well.
I’ve never bitten through a mouthpiece and never had to clamp my teeth down to feel that the second stage I was using was held securely in place.
The XL4 mouthpieces are retained with a reusable clip to make field replacement simple and easy.
To be fair, the octopus second stage doesn’t have a Comfobite, but then you’ll be handing that one to a less-discerning diver than yourself if the worst comes to the worst, and in a situation like that the receiving diver will be in no position to be picky over mouthpieces, and just needs to be grateful to have gas to breathe.
The second stages can be configured for left- or right-hand hoses. Each also features a +/- venturi control, pretty much standard equipment these days, and Apeks uses braided hose for better coldwater performance and lighter weight.

In the Water
From the very first breath I took, the XL4 was peachy. Smooth, quiet and easy to breathe as I swam along in a decent horizontal trim. I then tried my very best to upset it. I tried going head-down, doing slow forward and backward rolls, slow barrel rolls and lying face up.
All these manoeuvres resulted in nothing but the same easy breathe, and no trace of water through the exhaust.
Sticking my hands on a rock, I did a few minutes of hard finning to get my breathing rate up, and tried panting and taking huge gulping breaths to add to the gas-delivery requirement.
The XL4 didn’t care. It just did the job it was designed to do.
And when I got my breath back, I tried those tiny, gentle inhalations that you sometimes use when it’s a bright sunny morning and the fish are sparkling and the vis seems infinite and you’re feeling great and you only need to sip at the gas supply – and it coped just as well.
The T-pieces might look narrow but the exhaust bubbles didn’t make themselves a nuisance, and the purge button, pretty much the whole front of the reg, was easy to find, press and control. Exactly the same comments apply to the octopus reg, even if it doesn’t have a proper mouthpiece.

Conclusion
If you’re in the market, I don’t think you can go wrong with the XL4, and the only reason it hasn’t got the full 10 stars is that I haven’t tried it alongside the competition, and I’m not an ANSTI machine.

SPECS
PRICE: XL4 Stage 3 kit as tested £479
WEIGHT: 1200g
PORTS: 4mp, 1hp
DEPTH RATING: 80m
CONTACT: apeksdiving.com
DIVER GUIDE 9/10