When purchasing burettes, pipettes, volumetric flasks, or measuring cylinders, you will always see them listed as "Class A" or "Class B". This single designation determines the accuracy, price, and appropriate application of the glassware. Here is everything you need to know to make the right choice.
What Do the Classes Mean?
In laboratory glassware, accuracy class refers to how closely the delivered or contained volume matches the stated value. The tolerance is the maximum allowable error.
- Highest accuracy tolerances
- Individually verified and calibrated
- Certificate of conformance available
- Meets ISO 385, ISO 1042, ISO 835
- Permanent white enamel graduations
- For QC labs, pharmaceutical, research
- Tolerances twice those of Class A
- Batch verification (not individual)
- More economical
- Meets ISO 385, ISO 1042 (looser limits)
- Suitable for teaching and routine work
- For schools, universities, general labs
Tolerance Comparison by Product
Volumetric Flasks
| Capacity (ml) | Class A Tolerance (±ml) | Class B Tolerance (±ml) |
|---|---|---|
| 10 ml | 0.020 | 0.040 |
| 25 ml | 0.030 | 0.060 |
| 50 ml | 0.060 | 0.120 |
| 100 ml | 0.100 | 0.200 |
| 250 ml | 0.150 | 0.300 |
| 500 ml | 0.250 | 0.500 |
| 1000 ml | 0.400 | 0.800 |
Burettes
| Capacity (ml) | Class A Tolerance (±ml) | Class B Tolerance (±ml) |
|---|---|---|
| 10 ml | 0.020 | 0.040 |
| 25 ml | 0.030 | 0.060 |
| 50 ml | 0.050 | 0.100 |
Pipettes (One-Mark)
| Capacity (ml) | Class A Tolerance (±ml) | Class B Tolerance (±ml) |
|---|---|---|
| 1 ml | 0.006 | 0.012 |
| 2 ml | 0.006 | 0.012 |
| 5 ml | 0.010 | 0.020 |
| 10 ml | 0.020 | 0.040 |
| 20 ml | 0.030 | 0.060 |
| 25 ml | 0.030 | 0.060 |
| 50 ml | 0.050 | 0.100 |
When to Use Class A vs Class B
Use Class A when:
- Preparing standard solutions for calibration curves
- Pharmaceutical QC testing (GMP / pharmacopoeia requirements)
- Environmental analysis (water, food, soil testing)
- Research requiring traceable measurement uncertainty
- Preparing primary standards for acidimetry/alkalimetry
- Any work that will be cited in a scientific publication or regulatory submission
Class B is sufficient when:
- Teaching demonstrations and student practicals
- Rough volumetric measurements (±0.5% acceptable)
- Preparing non-critical dilutions
- School and college chemistry laboratories
- Industries where a ±0.5% volume error has no commercial consequence
International Standards Explained
The tolerance values listed above come from these international standards:
- ISO 385 — Burettes: defines Class A and Class B tolerances, graduation spacing, and tip specifications
- ISO 1042 — Volumetric Flasks: tolerance by capacity for both classes
- ISO 835 — Graduated Pipettes: tolerances for transfer and measuring pipettes
- DIN 12600 — German standard (widely accepted in Europe and Asia)
- ASTM E287 / E288 / E969 — American equivalents; slightly different numerical values
At Yash Instrument Company, all Class A products are manufactured to ISO tolerances and are also cross-referenced against DIN standards to ensure international acceptance.
Frequently Asked Questions
What is Class A glassware?
Class A glassware meets the highest accuracy tolerances defined by ISO, DIN, and ASTM standards. Each piece is individually calibrated and may come with a certificate of traceability. It is used for analytical and research-grade volumetric work.
What is the difference between Class A and AS?
"AS" (or "A Short Wait") designates Class A burettes that deliver the measured volume without waiting for drainage. They meet the same tolerance as Class A but are calibrated for immediate reading — useful in high-throughput labs. AS burettes have a larger bore tip.
Can I use Class B glassware for titrations?
Yes, for teaching purposes. For a student acid-base titration where a ±0.1 ml error is acceptable, Class B burettes work perfectly. For industrial QC or pharmaceutical titrations, always use Class A.
Is Class A glassware more expensive?
Yes — typically 40–80% more expensive than equivalent Class B, due to tighter manufacturing tolerances and individual verification. However, for critical analytical work the cost difference is negligible compared to the cost of an inaccurate result.
Does Yash Instrument Company supply both classes?
Yes. We manufacture both Class A and Class B burettes, volumetric flasks, and pipettes. Class A products are supplied with individual lot numbers for traceability. Bulk orders for schools (Class B) and export orders (Class A/B mix) are our speciality.
Need High-Quality Lab Glassware?
ISO-certified borosilicate glassware — made in Ambala, shipped worldwide.