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10L Round Bottom Boiling Flask - 3 neck 1 - 24/40 and 2 - 34/45
USA LabRBF10L3NECK$299.00Our 10L 3 Neck Round Bottom Boiling flask is constructed with 3.3 Borosilicate Glass and has 1-a 24/40 and 2 - 34/45 necks. Capacity: 10000mL / 10L Neck Size: 24/40 & 34/45 Necks: 3 SKU: RBF10L3neck We... -
5L Round Bottom Receiving Flask - 2 neck 24/40 and 34/45 Center
USA LabRBF5L2NECK-2434$170.00Our 5L 2 Neck Round Bottom Flask is constructed with 3.3 Borosilicate Glass and a 24/40 34/45 neck for a durable, common-size flask to use. Capacity: 5000mL / 5L Neck Size: 24/40 &... -
5L Round Bottom Receiving Flask - 3 neck 2 - 24/40 and 34/45 Center
USA LabRBF5L3NECK-2434$170.00Our 5L 3 Neck Round Bottom Flask is constructed with 3.3 Borosilicate Glass with 2 - 24/40 and 1 - 34/45 neck for a durable, common size receiving flask to use. Capacity: 5000mL / 5L Neck Size: 24/40 &... -
5L Round Bottom Receiving Flask - 2 neck 24/40
USA LabRBF5L-2NECK-2440$150.00Our 5L 2 Neck Round Bottom flask is constructed with 3.3 Borosilicate Glass and two 24/40 necks for a durable, common-size flask to use. Capacity: 5000mL / 5L Neck Size: 24/40 Necks: 2 SKU:... -
5000mL / 5L Round Bottom Receiving Flask - 1 neck 24/40
USA LabRBF5L1N$130.00Our 5L 24/40 1 Neck Round Bottom Receiving Flask is constructed with 3.3 Borosilicate Glass and has a 24/40 neck for a durable, common-size flask to use. Capacity: 5000mL flask Neck Size: 24/40 Necks: 1 SKU: RBF5L1N We ship all... -
2L Round Bottom Receiving Flask - 2 neck 24/40 2000ML
USA LabRBF2L2Neck$50.00Our 2000mL 2L 24/40 2 Neck Round Bottom Flask is constructed with Boro 3.3 Glass and a 24/40 neck for a durable, common-size flask to use. Capacity: 2000mL / 2L Neck Size: 24/40 Necks: 2 We ship all glassware products... -
2000mL Round Bottom Flask - 1 neck 24/40
USA LabRBF2L1N$40.00Our 2L 24/40 1 Neck Round Bottom Flask is constructed with 3.3 Boro Glass and a 24/40 neck for a durable, common-size 24 40 round bottom flask to use. Capacity: 2000mL Neck Size: 24/40 Necks: 1 We ship all glassware products with... -
1L Round Bottom Receiving Flask - 2 neck 24/40 1000ML
USA LabRBF1L2Neck$35.00Our 1000mL 1L 24 40 2 Neck Round Bottom Flask is constructed with 3.3 Borosilicate Glass and a 24/40 neck for a durable, common-size flask to use. Capacity: 1000mL / 1L Neck Size: 24/40 Necks: 2 We ship all glassware products... -
500mL Spherical Joint Round Bottom Receiving Flask - 1 neck 35/20
USA LabRBF500MLS35$30.00Our 500mL S35/20 1 Neck Spherical Joint Round Bottom Flask is constructed with 3.3 Borosilicate Glass and a 35/20 neck for a durable, common-size receiving flask to use. We ship all glassware products with additional care,... -
1000mL Round Bottom Receiving Flask - 1 neck 24/40
USA LabRBF1L1N$30.00Our 1L 24/40 One Neck Round Bottom Receiving Flask is constructed with 3.3 Borosilicate Glass and a 24/40 neck for a durable, common-size flask to use. Capacity: 1000mL Neck Size: 24/40 Necks: 1 We ship all glassware... -
500mL Round Bottom Receiving Flask - 1 neck 24/40
USA LabRBF500ML1N$25.00Our 500mL 24/40 One Neck Round Bottom Receiving Flask is constructed with 3.3 Borosilicate Glass and a 24/40 neck for a durable, common-size flask to use. Capacity: 500mL Neck Size: 24/40 Necks: 1 SKU: RBF500ML1N We ship all... -
500ml Round Bottom Receiving Flask - 2 neck 24/40
USA LabRBF500ML2NECK$25.00Our USA Lab 500ML Two Neck Round Bottom Receiving Flask is constructed with 3.3 Borosilicate Glass and a 24/40 necks for a durable, common-size flask to use. Capacity: 500mL Neck Size: 24/40 Necks: 2 SKU:...
Round-Bottom Flasks From USA Lab
Durable, Heat-Resistant Glassware for Distillation and Reaction Systems
Round-bottom flasks are the workhorses of any chemistry lab. Designed for uniform heating and smooth mixing, they're essential for distillation, reflux, and reaction setups. USA Lab offers a complete range of single-, double-, and triple-neck borosilicate flasks that deliver excellent heat resistance, strength, and precision.
Designed for Uniform Heating and Versatile Use
Borosilicate 3.3 Glass
Engineered to withstand thermal stress and chemical exposure to perform reliably during heating, cooling, and daily solvent use.
Multiple Neck Configurations
Choose from 1-, 2-, or 3-neck designs to suit your apparatus, making it easy to connect condensers, thermowells, addition funnels, or probes.
Ground-Glass Joints
24/40 and 34/45 standard taper joints ensure leak-free compatibility with common lab condensers, adapters, stoppers, and vacuum systems.
Heavy-Wall Options
Added strength for vacuum or high-temperature operations, providing extra confidence when working under reduced pressure or when uniform heating is essential for reaction control.
Compare Round-Bottom Flask Options
| Capacity | Models | Joint Sizes |
|---|---|---|
| 250mL | 1-Neck Flask 2-Neck Heavy-Wall Flask |
24/40 |
| 500mL | 1-Neck Flask 2-Neck Flask 1-Neck Spherical Joint Flask |
24/40 35/20 |
| 1L | 1-Neck Flask 2-Neck Flask |
24/40 |
| 2L | 1-Neck Flask 2-Neck Flask |
24/40 |
| 5L | 1-Neck Flask 2-Neck Flask 3-Neck Flask |
24/40 and 34/45 2 – 24/40 and 1 – 34/45 |
| 10L | 3-Neck Flask | 1 – 24/40 and 2 – 34/45 |
Practical Design for Reliable Operation
- Smooth curved base — Promotes even heat transfer and prevents localized boiling.
- Precision joints — Provide airtight seals for vacuum or distillation connections.
- Thick glass walls — Offer stability and durability under repeated thermal cycling.
- Easy compatibility — Pairs with USA Lab mantles, condensers, and adapters.
Choosing the Right Flask for Your Work
- Performing basic distillation or heating tasks? → A single-neck flask keeps things simple.
- Need access ports for thermometers or gas inlets? → Go with a double- or triple-neck design.
- Working at larger volumes? → Choose a 5L or 10L flask for high-capacity processing.
- Running under vacuum? → Use heavy-wall options for added safety and strength.
Why Choose USA Lab Round-Bottom Flasks
- Multiple neck and joint options for flexible configurations.
- Compatible with all standard USA Lab distillation and heating equipment.
- Supported by fast U.S. shipping and responsive technical help.
Equipment That Complements Your Round-Bottom Flasks
Pair your flasks with:
- Heating mantles to provide even, controlled heat
- Condensers to build complete reflux or distillation systems
- Stands and clamps to hold multi-neck flasks in place
- Vacuum pumps and cold traps to manage vapor flow and protect equipment
