3D-printed products and 3MF downloads from Roxium in Burlington, Ontario

Two spirals in one print: an outer shell that twists one way and a core that twists the other, turning past each other as you fiddle. Printed in a single colour it reads as one tapering cone; give the shell and the core a colour each and the two spirals separate in the eye as they turn, which is what the designer's own pictures show. The profile that prints it is 0.2 mm layers, 3 walls, 15 per cent gyroid infill, PLA, no supports, standing upright exactly as supplied.

Design by NerdHerder

An impossible passthrough built as a pyramid: the parts pass through one another and no amount of turning lets them go. 2.8" tall, about 21 g of plastic.

Design by BeninManc

An impossible passthrough shaped like an hourglass: two halves that turn through each other and stay locked together. 2.8" tall, about 24 g of plastic.

Design by BeninManc

A hard hat that goes on a keyring - the dome, the brim and the little ridge down the middle, printed in one piece with a hole through the top. 1.5" across, and it works as a key tag or a desk charm.

Design by astavr

A gyro fidget spinner: three curved rings interlock around a centre post and whirl as one, so it prints in a single piece with no bearings and no assembly - just flick it and go. The rings are loose in their track out of the printer, which is the part that takes a few tries to get right and the reason this one gets measured before it ships.

A flower-petal stencil 0.8 mm thin, for tracing or airbrushing onto paper, cake or a wall. 3.8" across, printed flat in one piece - thin enough to lie flush on the surface. Shown as a render, not a photo.

Design by Merilno3D

A hexagonal tube cut into one continuous spiral, so it springs and flexes in the hand and the turns of the helix roll past each other under a thumb. It prints as a single piece and needs no assembly, and it stands 2.8" tall by 1.3" across. Shown as a render, not a photo.

Design by NerdHerder

The topsy tail tool: a loop on a stem that pulls a ponytail through itself, so you can make the flip without a second pair of hands. 7.0" long, printed flat in one piece. Shown as a render, not a photo.

Design by Cy-Bea

A frog that jumps: press its back and it springs off the table, and the pond bowl catches it. Pick the frog on its own or the bowl with it - the bowl is 5" across, and three frogs fit on one plate if you want a set. Shown as a render, not a photo.

Design by Niski