Test Tube Stoppers, LDPE, Blue, BD® Compatible — 300-2912-B20 | 1000/Bag | Caplugs® Evergreen

Test Tube Stopper Caps for 12 mm Test Tubes, LDPE, Blue — 300-2912-B20 | 1000/Bag

Technical Narrative

The Caplugs® Evergreen is a blue LDPE stopper cap for 12 mm OD test tubes — a plug-in friction-fit closure designed for 12 mm OD test tubes — a very widely used diameter across clinical, research, and culture tube formats. The 12 mm size covers clinical chemistry, hematology, microbiology, and research tube capping across the widest range of laboratory tube formats. Blue stoppers mirror the CLSI H3 convention where blue-top tubes indicate citrate anticoagulant — making blue stoppers a natural choice for post-collection blue-top tube closure and for designating citrate specimen batches in color-coded routing systems.

LDPE's low-density flex modulus allows the stopper plug to compress under insertion and spring back against the tube inner wall, providing retained friction-fit closure without the brittleness of rigid materials at the repeat insertion/removal cycles of clinical and research tube workflows. LDPE retains this flexibility from -20°C frozen archive through 60°C incubation — maintaining stopper retention through freeze-thaw cycles and incubation without hardening or losing friction-fit engagement. LDPE is chemically inert to urine, serum, plasma, broth media, and standard aqueous buffers — no leaching into tube contents during storage.

At $44.13 per 1000/Bag — $0.0442 per stopper — the delivers 12 mm blue tube closure at per-stopper economics for high-volume programs. Also available in this size: 300-2912-E20 (Orange 12 mm ($44.13)); 300-2912-G20 (Green 12 mm ($44.13)); 300-2911-020 (Natural 11 mm ($48.09)).

Technical Specifications — Caplugs® Evergreen

Test Tube Stopper Application Compatibility —

The 12 mm blue LDPE stopper cap is designed for 12 mm OD test tubes — a very widely used diameter across clinical, research, and culture tube formats. Compatible workflows:

Always validate stopper fit with your specific tube brand before bulk purchase — 12 mm OD tubes vary in opening diameter by wall thickness. Request a free sample to confirm friction-fit retention before volume commitment.

Chemical Resistance — Low-Density Polyethylene (LDPE)

LDPE provides the flexibility essential for stopper-format tube caps and broad chemical inertness to standard laboratory specimen matrices.

Laboratory Applications

The serves clinical and research microbiology programs capping culture tubes during incubation; clinical chemistry and hematology labs archiving specimen tubes; research labs capping buffer and reagent stock tubes; cell culture programs requiring sealed tube incubation; and any laboratory workflow requiring friction-fit closure on 12 mm OD test tubes.

U.S. Manufacturing, Quality & Institutional Procurement

Every Caplugs® Evergreen lot is precision-molded at our California manufacturing facility and subject to rigorous dimensional inspection and material purity verification. We supply reference laboratories, hospital systems, and federal procurement offices under institutional pricing programs with blanket-order support and same-day shipping. Request a free sample below to validate stopper fit with your tube brand before committing to volume.

Frequently Asked Questions — Caplugs® Evergreen

What test tube formats use 12 mm OD and fit the stopper?

The fits 12 mm outer diameter test tubes. Compatible formats include: Standard 12 × 75 mm, 12 × 100 mm glass and PS culture tubes, BD Vacutainer-compatible collection tubes, and common clinical polypropylene test tubes. Always validate stopper-to-tube fit with a sample set before bulk purchase — tube opening diameter varies within the 12 mm OD range depending on glass or plastic wall thickness. Request a free sample to confirm friction-fit retention before committing to volume.

What are the color conventions for 12 mm tube stoppers — Blue, Orange, and Green?

All three 12 mm LDPE stopper colors are identical in material and friction-fit performance — the difference is color routing only. Blue : mirrors the CLSI H3 blue-top citrate anticoagulant convention — used to designate citrate specimen batches or post-collection closure of blue-top clinical tubes. Orange (300-2912-E20): high-visibility designation for STAT or priority specimens — orange stoppers stand out immediately in loading racks for urgent specimen routing. Green (300-2912-G20): general color-coded specimen-type or batch designation. Choose color based on your laboratory's tube routing color-coding protocol.

Why is LDPE specified for test tube stopper caps rather than PP or PS?

Stopper-style caps require a material with sufficient flex modulus to compress under insertion and spring back for friction retention — without fracturing under repeated use. PP and PS are too rigid and crack under the repeated insertion/removal forces of high-volume tube workflows. LDPE's low-density flex allows thousands of insertion/removal cycles without fracture, retains flexibility at -20°C to prevent brittle failure during frozen archive stopper removal, and provides chemical inertness to clinical specimen matrices (urine, serum, plasma, broth).