Quick answer
Luer-lock syringes have a threaded collar the needle screws into; luer-slip needles push on and hold by friction. For mixing and drawing up, where you swap a blunt drawing needle for the hub of a filter or a vial adapter, luer-lock is the one that does not pop off under pressure. For injecting small amounts, a fixed-needle insulin syringe beats both: no connection at all, and almost no dead space.
Side by side
Rows that differ are highlighted. Values come from the product records for the two products named in the header.
Luer-lock Luer-Lock Syringes, 3 mL |
Fixed needle (insulin) Insulin Syringes 31G, 0.5 mL (100-count) |
|
|---|---|---|
| GaugeNeedle thickness. A higher number is a thinner needle: 31G is thinner than 30G. Glossary | — | 31G |
| CapacityHow much liquid the barrel holds. Smaller barrels have more space between the lines, so small amounts are easier to read. Glossary | 3 mL | 0.5 mL |
| MarkingsU-100 means 100 units to the millilitre, so one unit is 0.01 mL. A mL scale is marked in tenths. Glossary | mL | U-100 |
| Smallest lineWhat one line on the barrel is worth. Half-unit lines let you read 0.005 mL; a 1 mL syringe is usually marked in 2-unit steps. Glossary | 0.1 mL | 1 unit |
| Needle lengthLength of the needle. 4–8 mm is the usual range for under-the-skin use; longer is for muscle. Glossary | — | 8 mm |
| Needle connectionFixed means the needle is built in (least dead space). Luer-lock screws on and cannot pop off. Luer-slip pushes on. Glossary | Luer-lock | Fixed needle |
| Needle included | No | Yes |
| TipBlunt tips draw liquid from a vial without being able to go through skin; they are for mixing and drawing up. | None | sharp |
| Dead spaceLiquid left in the hub after the plunger bottoms out. Fixed-needle insulin syringes have almost none. Glossary | standard | low |
| PriceRough position within its category, not a live price: budget is the cheapest sensible option, premium costs more for a reason the page explains. | Budget | Budget |
| TravelWhether it is practical to fly with: carry-on means it goes through security without fuss. | Carry-on friendly | Carry-on friendly |
| SterileIndividually sealed and sterile until opened. Anything that touches the inside of a vial or your skin should be. | Yes | Yes |
| PackHow many you get. Check this against the photo; Amazon listings often show ten and ship one. | 100 | 100 |
| Reusable | No | No |
Which should you choose?
- Pick luer-lock for mixing, filtering and nasal-spray filling: the needle cannot come off when you push.
- Pick a fixed-needle insulin syringe for injecting: least dead space, finest needle, one piece.
- Avoid luer-slip for anything under pressure; it is fine for oral syringes and rinsing, not for a 0.22 µm filter.
The products
Open in the comparison tool Find the right syringe
Related guides
- Luer-lock vs luer-slip syringes: which to buy
- Mixing (reconstituting) a vial, step by step
- Air bubbles in a syringe: how to get rid of them
Common questions
Can a luer-slip needle fit a luer-lock syringe?
Physically yes; it pushes on without engaging the thread, so it can still pop off. Use luer-lock needles on luer-lock syringes.
What does 'luer' mean?
It is the standard taper on syringe tips, named after its 19th-century inventor. Every luer needle fits every luer syringe of the same type.
Reviewed 2026-09-03. Equipment comparison only; nothing here is advice about what to inject or how much. Affiliate links open your own country's Amazon store; your price is the same.