Most dive bezels are one colour because they only have one job. This one is two, and the reason is genuinely clever: it's a 24-hour scale, split black and white, so a glance tells you whether it's day or night wherever your second time zone is. Omega calls it the world's first polished bi-ceramic bezel, collectors call the watch the Oreo, and it sits on a 43.5mm Planet Ocean with a black ceramic dial and 600 metres of water resistance.
Reference 215.30.44.22.01.001 is the steel GMT version of the Planet Ocean — a different watch from the three-hander it shares a case with, and one that asks a different question of a strap.
The size: 21mm
The 43.5mm Planet Ocean takes a 21mm strap. A hands-on review of this exact GMT gives 21mm at the lugs, and a specialist dealer's measurement of the 43.5mm case in the same generation returns 43.5mm across, 49mm lug-to-lug and 21mm between the lugs.
This is the number the Planet Ocean line most often gets wrong, because the range spans four sizes and four widths: the 39.5mm takes 19mm, the older 42mm takes 20mm, this 43.5mm takes 21mm, and the 45.5mm takes 22mm. Owning two Planet Oceans almost never means owning one strap size.
Two things on our product pages: the width dropdown opens on 19mm, so change it to 21mm before adding to cart, and the buckle selector defaults to "No Buckle" — add one if your watch came on the bracelet. Black is the right choice on this watch.
A bezel that separates day from night
It's worth understanding what Omega actually built here, because it's the whole reason the watch exists.
A GMT hand tells you the hour somewhere else, but on a 24-hour scale the number alone doesn't tell you whether that hour is breakfast or midnight. Omega's answer was to make the bezel itself carry the information: a bi-directional 24-hour bezel in polished ceramic, split into a black half and a white half, with the numerals and scaling in contrasting colours. Read the GMT hand against the white and it's daytime there. Against the black, it isn't. No mental arithmetic.
That bezel was the first of its kind — two ceramics polished together into one ring, which is harder than it sounds and is why nobody had done it before.
The rest is Planet Ocean proper. The dial is black ceramic with applied Arabic numerals, a date at 3 and a central GMT hand. The case is 43.5mm of brushed and polished steel with the collection's twisted lyre lugs, a screw-down crown and a helium escape valve, and it runs to 600 metres. Inside is the calibre 8906, a METAS-certified Master Chronometer. Lug-to-lug is 49mm, so it wears every bit of its size.
For orientation: Omega built an earlier Planet Ocean GMT on this case with a plain black ceramic bezel and a different movement, and this same bi-ceramic model was also sold on a strap rather than a bracelet. Everything below fits all of them.
Omega lined the leather with rubber
Here's the detail that settles the strap argument, and it comes from Omega's own product descriptions.
The strap version of this watch didn't ship on plain leather. It shipped on black alligator leather with a moulded rubber lining — because a 600-metre dive watch with a helium escape valve is going to meet water, and leather alone can't do that. Omega knew it, and engineered a compromise: the look of leather on the outside, rubber against your skin.
You don't have to compromise. A rubber strap is what that construction was reaching for, without the half of it that cracks. It also solves the practical problem this watch actually has: at 43.5mm across and 49mm lug-to-lug on a bracelet with substantial end-links, the case reaches a long way before anything starts to bend. Rubber starts curving at the lug.
The best straps for the Planet Ocean GMT
1. Black with a white line — the bezel, continued
The single most on-the-nose-correct pairing on this blog. The watch's defining feature is a ring split into black and white; a black strap with a white centre line is those same two colours in the same relationship, running the length of your wrist. Black ground, one white element, nothing else — it makes the bezel read as a design decision rather than a technical quirk, and it's the configuration that photographs best because the eye connects the strap to the bezel instantly. Start here.
2. Full black — side with the night
The disciplined version. A full black rubber strap puts black dial, black bezel half and black strap into one continuous dark object, which leaves the white half of the bezel as the only bright thing on the entire watch. That's a strong look on a monochrome design, and it's the most wearable strap here for a case this large — dark straps read smaller than pale ones. The everyday answer.
3. Navy blue — the travelling colour
A watch built around second time zones is a watch that goes places, and navy is the colour that handles that best. A navy blue rubber strap is dark enough to keep the bezel as the focus but noticeably warmer than black under a jacket sleeve, and it's the one option here that doesn't fight a black-and-white design — navy is the classic third colour alongside those two. The pick for owners who wear this watch to airports rather than into the sea.
4. Black with an orange line — the family colour, restored
Orange has been the Planet Ocean's signature since 2005, and this reference doesn't have a trace of it — the bi-ceramic bezel spent its colour budget on black and white instead. A black strap with an orange line hands it back below the case, where it flags the watch as a Planet Ocean without touching the bezel's day-night logic above. The pick for anyone who bought into the line rather than just this model.
The short version
21mm — not the 20mm of the 42mm models or the 22mm of the 45.5. Black-and-white to echo the bezel, full black to side with the night, navy for travelling, orange to bring the family colour back.
Every strap in our Planet Ocean collection ships with spring bars included and carries a lifetime warranty on rubber — with free worldwide shipping and no import costs, part of why more than 50,000 customers have trusted us with their watches. Guides to every other Omega we've covered live in the Omega strap guide hub. Omega built a bezel that knows day from night. Give it something that handles both.
