The Large Gravitron is the one everybody photographs. The Medium is the one people actually keep. Nine inches instead of eleven, three and a quarter across instead of a footprint that owns the whole side table, and the identical closed-system pull that made the shape famous in the first place. GRAV didn't soften the mechanic to shrink it — they just built the same thing at a size that fits a normal apartment.
The GRAV Medium Gravitron is a glass gravity bong: a 9-inch bottle-and-base system in 5mm borosilicate, sealed at the waist with a platinum-cured silicone grommet, with a 14mm female joint and a GRAV 14mm funnel bowl included. It sells for $79.99 and holds roughly a half gram per bowl.
Gravity is doing the work, so the technique is the product. Fill the base about halfway. Pack the funnel bowl, seat it in the joint at the neck, light it and lift the bottle at the same time — steady, not fast. The rising bottle leaves a vacuum, and the vacuum pulls smoke into the chamber behind it. Once the bottle is loaded, pull the bowl, put your mouth on the neck, and push down.
The water displaces everything upward in one pressurized motion. It's a closed system start to finish, so nothing wanders off into the room between the lighter and your lungs, and that's the reason a half-gram bowl in a Gravitron goes further than a half-gram bowl anywhere else.
Five-millimeter borosilicate is the number that matters on this piece. The original Gravitron was thin, and thin glass on a device you lift and reseat every single hit is a countdown. The 2.0 generation went to 5mm across the line, and it changed the ownership experience more than any other spec — you stop treating it like it's fragile, which is the only way a gravity bong actually gets used.
The flange at the top of the neck is the companion fix: a hard lip for your fingers, so the lift doesn't depend on gripping wet, smooth glass.
The grommet is the part that fails on knockoffs. GRAV specs platinum-cured silicone, which holds its seal and its shape through repeated compression better than cheaper stock, and which cushions the one place where bottle glass and base glass would otherwise grind. A gravity bong with a tired grommet doesn't break dramatically — it just starts leaking, the pull goes soft, and you assume the piece is worn out when it's a five-dollar ring.
Here's the practical case for the Medium over the full-size Gravitron 2.0, beyond the obvious. The Medium runs a 14mm joint. The 11-inch version runs 18.8mm. Fourteen is the industry-standard size, which means every spare bowl in your drawer already fits, every ash catcher and banger on the shelf at the shop already fits, and you will never once order the wrong replacement.
That is a genuinely underrated reason to size down. The Medium's chamber is smaller, so the hit is smaller — that's the honest trade, and for most people it's the correct one.
Who this is for: flower smokers who want the gravity mechanic as a regular thing rather than a party trick. The Gravitron asks for two hands and your attention; there's no sipping at it while you do something else.
If you want a piece you can run absentmindedly, the Oracle or the Small Wide Base are the ones to look at. If you like the gravity idea but want more glass around it, the Monarch is GRAV's elaborated take on the same physics.
The Gravitron's cultural position is unusual for cannabis hardware — it's one of the few pieces recognized well outside the shop. The bottle-in-a-bucket hack is older than the company, but GRAV was the one that treated it as a design problem worth solving in borosilicate, out of Austin, with the same airflow-first thinking they apply to their science glass.
What you're paying for over a knockoff is the tolerance between bottle and base. That gap is the entire mechanism: too tight and the bottle sticks halfway through a pull, too loose and it vents. Cheap copies get it wrong in both directions. See the full range on the GRAV Labs brand page.
Specs
- Type: Gravity bong (glass water pipe)
- Height: 9 inches
- Width: 3.25 inches
- Material: Borosilicate glass, 5mm thick
- Seal: Platinum-cured silicone grommet
- Joint: 14mm female
- Included: GRAV 14mm funnel bowl
- Bowl capacity: About a half gram
- Neck: Flanged grip for lifting
- Intended for: Dry flower
- Price: $79.99
Cleaning is the easy part of owning one. The bottle is an open tube with no percolator to clog, and the base is a wide cylinder your hand fits into. Pull the grommet before soaking anything in isopropyl, and let it dry completely before you reseat it — a damp ring seats crooked and leaks, and the glass gets blamed for it.
Buy it if you want the real Gravitron pull on a standard 14mm joint at a size you'll leave out on the counter. For adults 21+.