What is the Open Basing System (OBS)?

The Open Basing System (OBS) is an open standard for wargaming bases: one universal set of sizes whose dimensions are public, so anything built to it fits everything else built to it. On that standard we make the range: injection-moulded ABS bases, ABS and 3D-printed converters, printed bases up to 300 mm, movement trays and tray adapters, flying bases, hero bases, STL files for your own printer, and the Base Builder for custom bases and trays. It has been in active development for several years, and it is still growing.

Looking for the base a particular model needs? That lives in the base size tables by game and the guide to choosing a base size. This page is about the system itself, and which part of it you need.

What problem does OBS solve?

Bases that don't fit with each other. Not every base on the market is made to the standard sizes, and a model on an off-spec base can't use the converters, trays and display bases made for everyone else unless you take it off and rebase it.

Some bases come out a little too wide, some a little too tall. On their own they look fine; the trouble starts when you try to pair them with anything else. We regularly hear from customers whose bases won't go into a standard converter or tray, and by then the only fix is a hobby knife and a fresh base.

A shared standard takes that problem away. A model on a 25 mm OBS round can drop into a converter to play as 32 mm, rank up in a tray adapter as part of a square unit, then sit on a hero base for the cabinet, and its original base never comes off.

What makes OBS open?

The dimensions are public. Most of our physical listings carry a dimensioned drawing, and the files are available as STL bundles for a token price, so anyone can build to the same standard.

An open standard here means sizes that are written down, published and kept to, so that anyone (us, another maker, or you at your desk with a 3D file open) can make a part that fits everything else built to them.

Why publish them? So that when you copy the sizes into your own 3D file, you get them right, and whatever you make (a base, a tray, a scenic plinth) still pairs with every converter, tray and display base built to the standard. No ripping models off, no rebasing. OBS is for you, the hobbyists, not for us, which is why the data is open to everyone. The guide to choosing a base size also lists what our standard rounds actually measure, straight from our CAD.

Can I print OBS myself?

Yes. There are three STL bundles: Core (745 designs), Converters (315 designs) and Hero Bases Display Extenders. Each comes with a choice of licence:

• Regular is for personal use: printing for your own models.
• Commercial lets you sell what you print and includes reseller permission.

Both give you one year of downloads and updates; to keep getting updates after that, buy the pack again. The files are designed for FDM printing.

Core holds the base families (round, square, rectangle, oval, pill, hexagon, octagon, triangle, flying bases and stems) in plain, hollow, slotted, reinforced and wide-lip versions where the shape allows. Converters holds the size and shape converters: round, square, oval and rectangle, including from one shape to another. They are built to OBS dimensions, so they may not fit off-spec bases.

What is in OBS today?

Nine families of parts, made three ways: moulded in ABS, 3D printed in PLA or PETG, or supplied as STL files. All of them follow the same dimensions. Together that comes to about 2,300 physical SKUs.

The moulded ABS bases are the backbone: the standard wargaming sizes, with several million kept in stock for retail and wholesale customers. Printing fills in everything a mould doesn't reach: unusual sizes, big footprints, hollow bases for water effects, pill shapes and more.

Flying bases follow the same idea: a clear base with a plug-in stem, and spare stems and bases sold separately, so a snapped stem doesn't mean a new base.

What are base converters for?

A converter changes the size or shape of a base without rebasing. You press the model's existing base into it and it plays as the bigger size, held by a tight fit, with no glue and no magnets; an opening underneath lets you push the base back out.

That covers the usual reasons: a rules update moved your unit up a size, a squad needs to match a newer kit, a character in your D&D party grew, or a heavy model wants a wider footprint so it stops falling over.

There are two kinds:

• ABS converters are injection moulded, in round, square and rectangle sizes. As far as we know, nobody else mass-produces injection-moulded base converters, and the range keeps growing.
• Printed converters cover the sizes and shapes the moulds don't, printed to order with the same push-out design.

How do movement trays and tray adapters fit OBS bases?

Movement trays are cut to OBS footprints, so OBS bases drop straight in. Tray adapters do for a whole unit what converters do for one model: round bases sit in round recesses, the outside is square, and the unit ranks up with square-based units.

The whole regiment lifts as one piece, nothing is glued to the models, and they come back out for the next game that wants rounds. It is the simple answer to round-based models in a game that wants square ranks.

What are hero bases?

A hero base is a display extender: it turns a gaming base into a display base or plinth. The model stays on its normal base, sits on the extender for the cabinet or a painting competition, and lifts off again for the table.

They started as STL files and are now printed by us as well, in round/oval and square/rectangle versions, from low stepped display bases to taller plinths.

What is the Base Builder?

The Base Builder is a page where you design a base or a movement tray yourself and we print it. Between them, those two modules already give you more than 140 billion different bases and trays, and more than 180 billion once you pick the material and finish.

For a base you choose the shape (round, square, rectangle, oval, pill, hexagon or triangle), any size from 10 mm up to 290–300 mm in 0.1 mm steps, a height between 3 and 10 mm, an open or closed underside with your wall thickness, straight or sloped sides, and the material: smooth PLA, smooth PETG or textured PETG. For a movement tray you set the inside length and width (10–296 mm), the rim width and height and the floor thickness, and it is printed in black PLA. If a game, a scratch-build or an old metal model needs a size nobody lists, this is where to get it.

It is the newest part of OBS and the seed of something much bigger: it is being extended from bases and trays to the rest of the range, with the aim of removing most of the limits on what a base can be.

Moulded or printed: what's the difference?

Moulded ABS bases come in fixed sizes, are kept in stock in large numbers and are the cheap way to base a lot of models in a standard size. Printed bases come in almost any size up to 300 mm and in shapes a mould can't justify, printed to order in PLA or PETG. Both are built to the same dimensions.

A mould is a big investment, so new ones arrive at about 8 a year and printing covers everything they haven't reached yet. The printed range is already in the thousands of SKUs, and since our bigger printers arrived with 300 mm build plates, the top end has moved up to 300 mm.

Basing a whole army in standard sizes? Start with moulded. Need one odd size, a big centrepiece base or a special shape? Go printed, or straight to the Base Builder.

Why is OBS a system and not just a range of bases?

Because a standard is only worth something if every size keeps to it, including the ones that don't sell much. We design every base as part of one system, with the same features, quality and standard, and we look after the unpopular sizes as well as the bestsellers.

Most shops resell bases: they stock the sizes that sell, leave the rest, and don't spend money keeping old moulds up to date. For them that is the sensible choice. A mould for a less popular size can take about five years to pay for itself, and for a normal retailer that makes no sense at all. So the common sizes are easy to find, and the odd ones are an afterthought.

For us the same mould does make sense, because we don't judge sizes one at a time. The strong sellers help pay for the weaker ones, so the less popular sizes still get moulds, updates and the same standard as the rest, and converters, trays and hero bases fit them too. It is the least spectacular part of the job, done steadily and continuously.

The effect for you: a range that only pays for its bestsellers gives you the popular sizes and never anything new or better. OBS will, over time, cover every size there is real demand for, all to the same standard and all fitting each other.

How does OBS keep growing?

On several planned tracks at once. Next on the bench are new plinths, display bases, display movement trays and a handful of smaller ideas, with no dates and no promises.

The tracks: new ABS moulds, a growing ABS converter range, more printed sizes and shapes, physical hero bases, the STL bundles, and the Base Builder. The honest trade-off is that every week spent widening the existing ranges is a week not spent on brand-new products, so new things arrive a little slower than we would like.

Buying from the shop is what funds the whole project: an order for plain 25 mm rounds also helps keep the odd sizes alive. We're a small company, and the software subscriptions and licences behind the design work aren't cheap.

If there is a size, shape or part you'd like to see, email customersupport@hobbyheaven.org or leave a comment under this post. What has changed so far is in the OBS changelog.