Pen Tips
Picking a tip: what actually changes.
Tips are the cheapest part of the setup and the one that most affects how the pen feels to use. Get the tip wrong and a perfectly good pen feels stiff, slow, or drippy. This page explains what each number on the box does, so you can buy on something better than guesswork.
1. What fits
MODTECH pens accept standard universal screw-on pen needles — the same fitting used by the great majority of dial-style pens. There is no proprietary thread and no adapter to hunt down. If the box says universal screw-on pen needles, it will thread on.
On the box and on Amazon they're sold as pen needles. We call them tips. Same thing.
We don't sell tips
MODTECH supplies pens and sterile cartridges. Tips are not included and we don't stock them. That's deliberate — they're a commodity, they're stocked everywhere, and you shouldn't be locked to one supplier for a consumable.
This page is a buying guide, not a product page. The guidance below is the same whether you buy through our links or not — see section 7 for exactly what we earn and how.
2. Gauge
What the number means
Gauge describes the outside diameter of the needle, and the scale runs backwards from what you'd expect: a higher gauge number means a thinner needle. A 32G is finer than a 29G.
| Gauge | Relative size | Trade-off |
|---|---|---|
| 29G – 30G | Thicker | Easiest flow, handles viscous solutions, widest outside diameter |
| 31G | Middle | The usual compromise — fine, still flows readily |
| 32G – 33G | Finest | Finest outside diameter, slowest flow, first to clog |
Gauge and flow
Flow through a narrow tube falls away sharply as the tube gets narrower — far faster than the change in diameter suggests. Going a couple of gauges finer doesn't make the pen slightly stiffer, it can make it dramatically stiffer.
If your pen suddenly feels hard to press and nothing else changed, the tip is the first thing to suspect.
3. Wall thickness
Regular, thin wall, extra-thin wall
Gauge only tells you the outside. What the fluid actually travels through is the inside — the lumen. Two needles can share a gauge and have noticeably different bores depending on how thin the manufacturer made the wall.
| Regular wall | Standard bore for its gauge. Cheapest, most common. |
| Thin wall | Wider bore for the same outside diameter — better flow at the same fineness. |
| Extra-thin wall | Widest bore for the gauge. Usually the priciest. |
Why this beats chasing gauge alone
A 32G extra-thin-wall tip can flow about as freely as a thicker regular-wall one. That's the whole trick: you keep the fine outside diameter and get the bore back.
If you want fine and easy to press, buy on wall thickness rather than dropping to a bigger gauge. It's the single most useful thing on this page.
4. Length
The common sizes
Pen needles are typically sold in 4mm, 5mm, 6mm, 8mm and 12.7mm. All of them thread onto the pen identically — length has no bearing on whether a tip fits.
Which length is appropriate for a given application is not something we advise on. MODTECH sells hardware, and needle length selection sits outside what we can responsibly comment on. Below is the hardware side only.
Length and dead space
A longer needle holds slightly more solution inside it after you dispense. It's a small amount, but it's part of the residual volume you never recover, and it matters proportionally more when your per-session amount is small. Shorter tips hold back marginally less.
5. Coating
Why tips are coated
Most pen needles carry a thin silicone coating that reduces friction. It's applied in manufacturing, it's microscopically thin, and it is largely spent after a single use.
This is the practical reason a reused tip feels worse than a fresh one: the coating is gone, and the point itself is no longer as clean as it was. A tip is a one-session consumable, and treating it as one costs pennies.
6. Matching tip to solution
Thicker solutions
The more viscous your solution, the more the tip's bore matters. If a fine tip is producing a stiff, slow dispense, you have two levers: step down a gauge, or stay at your gauge and move to a thin-wall or extra-thin-wall tip. The second usually gets you what you want without giving up fineness.
Straight from the fridge
Cold solution is thicker solution. A pen taken straight out of the refrigerator will be noticeably harder to press than the same pen twenty minutes later.
If yours feels stiff first thing, let it sit and come up to room temperature before you decide the tip or the pen is at fault.
7. Where to buy tips
Everything above is about picking the right tip. This section is about getting hold of them — but there are three habits worth settling first, because they matter more than which box you end up with.
Three rules that cover most problems
- Fresh tip, every session. No exceptions. It's the cheapest reliability you'll ever buy.
- Take the tip off when you're done. Leaving one on invites drips, lets air work its way back in, and leaves an exposed sharp on a pen going into a fridge.
- Used tips go straight into a sharps container. Not the bin, not a jar, not loose in a drawer.
Rule one is also the reason it's worth buying in quantity. A hundred-count box is not an extravagance if you're using one a session.
Five places to start
We still don't sell tips, and we're not going to start. But "go find some universal screw-on pen needles" is a thin answer to a fair question, so here are five places on Amazon that carry them in the gauges, wall thicknesses and lengths this page describes — four brand storefronts and one specific product. Check the box for gauge, wall and length before you commit to a hundred of anything.
Disclosure: the five links below are Amazon affiliate links. If you buy through one, we earn a small commission from Amazon. It costs you nothing extra — the price is the same whether you use our link or search Amazon yourself.
As an Amazon Associate, MODTECH Supply earns from qualifying purchases.
- BD Ultra-Fine Nano 2nd Gen 32G × 4mm, 90 count. The fine-gauge benchmark, with a wide base that sits flat and steady. Priciest per tip of the five.
- The Verifine Universal screw-on pen needles across the common gauges and lengths. A sensible first stop if you haven't settled on a brand yet.
- ONE-CARE A dedicated pen tip range in the usual sizes, including the finer gauges. Straightforward listings that state gauge and length clearly.
- EasyTouch Long-running budget brand with a wide spread of gauges and lengths. Easy to find in larger count boxes, which suits rule one.
- Medt Multi-pack boxes at the lower-cost end. Worth a look if you go through tips quickly and don't need a premium label.
Links open on Amazon. Prices, stock and specifications are Amazon's and change without notice — always confirm the gauge, wall thickness and length on the listing itself.
What this does and doesn't change
None of the guidance above this section changed when we joined the affiliate program. Wall thickness still beats chasing gauge, cold solution is still thicker solution, and if you find the same tip cheaper somewhere else, buy it there.
These links go to Amazon, not to us. We never see your order, so anything that happens on Amazon's side — delivery, returns, product questions — has to go through Amazon and the seller.
Safe handling and disposal Pen feels stiff? Start here
8. Where to go next
- How It Works: Set up and load your pen
- Pen models
- Cartridge information
- Troubleshooting
- Safety and warnings
- Full FAQ
Still stuck?
Email tfortech@modtechsupply.net. We reply within one business day.
MODTECH products are precision hardware sold for laboratory and research use only. They are not medical devices. No substances are included with or sold alongside any product, and nothing on this page constitutes medical advice or instructions for administering any substance to humans or animals. Third-party brands are named for compatibility reference only and are not affiliated with or endorsed by MODTECH.
Some links on this page are affiliate links. As an Amazon Associate, MODTECH Supply earns from qualifying purchases; you pay nothing extra. Amazon and the Amazon logo are trademarks of Amazon.com, Inc. or its affiliates.