GL18, White, Self Seal Closure

This closure is compatible with all GL18 glass dropper bottles in the BlueSky range, including 5ml, 10ml, 15ml, 20ml, 30ml, 50ml, and 100ml sizes in both amber and clear glass. GL18 (also known as NW18 or DIN168) is an internationally standardised neck finish — the inner bore diameter of 10.65mm ± 0.15mm is consistent across all bottle volumes, so the same closure fits the entire range without modification.

A self-seal closure contains an integrated membrane inside the cap that compresses against the bottle rim on closing, creating a hermetic seal without a separate liner insert. A flat-lined cap uses a distinct liner disc — typically foam or a composite material — to create the seal. Self-seal closures simplify the capping process and are suitable for most cosmetic and personal care formulations. For formulations requiring enhanced oxygen, moisture, or chemical barrier protection, a flat-lined cap with a specialist liner (PET, aluminium, PVDC, or Teflon) may be more appropriate. Contact BlueSky’s team to discuss which option best suits your formulation.

Yes. The GL18 White Self-Seal Closure is compatible with the full range of GL18 dispensing accessories available from BlueSky, including vertical droppers (for precise pharmaceutical oral dosing), rim droppers (for general dispensing of essential oils and cosmetic serums), pourers, orifice reducers, and syringe inserts. All accessories fit within the GL18 neck and work across all four cap shapes in the system.

The standard screw cap is appropriate for cosmetic, personal care, and general-use formulations where tamper evidence is not a regulatory or commercial requirement. If your product requires visible first-open evidence — for example, for retail distribution or consumer confidence — BlueSky’s OVII (integral tamper-evident ring) or OVIII (assembled tamper-evident ring) caps are available within the same GL18 system. For products requiring child resistance under ISO 8317 — such as household medicines or OTC pharmaceutical preparations — the CRC cap is the appropriate choice. All options use the same GL18 neck, so changing closure type does not require a change of bottle.