# item.guide
Side-by-Side Comparison Pens, Inks & Leads

Parker G2 Refill vs. Fountain Pen Cartridges

Comparing 2 standards across 13 specifications. 13 key differences identified.

Comparing:
Parker G2 Refill
Fountain Pen Cartridges

The Parker-Style G2 Refill (standardized under ISO 12757-2 Doc G2) is one of the most widely adopted ballpoint and gel pen refill standards. Measuring 98.1 mm in length and 5.8 mm in body diameter with a stepped metal barrel and grooved plastic crown cog, it is used by hundreds of luxury pen brands and custom machined EDC pens.

View full Parker G2 Refill spec sheet →

Proprietary Fountain Pen Cartridges are brand-exclusive ink formats engineered with unique nozzle diameters and collar locking geometries that are incompatible with Standard International pens. Key proprietary systems include Pilot/Namiki (wide 5.5 mm bore), Lamy T10 (stepped collar), Sailor (flared collar), and Platinum (metal ball seal).

View full Fountain Pen Cartridges spec sheet →

Specification Comparison Table

13 Parameters
Parameter / Spec
Overall Length
98.1 ± 0.3 mm (3.86 in)
Main Body Diameter
5.8 ± 0.1 mm (0.228 in)
Stepped Tip Diameter
2.5 mm extending 18.0 mm from barrel shoulder
ISO Standard Code
ISO 12757-2 Type G2 (Documentary permanence proof)
Crown Cam Geometry
Molded nylon cog crown with 4 radial guide splines for push-button advance mechanisms
Available Ink Formulations
Oil-based ballpoint (Parker QuinkFlow, Schmidt P900), hybrid low-viscosity (Uni Jetstream SXR-600), gel ink (Schneider Gelion+, Itoya)
Pen Brand Compatibility
Parker, Pelikan, Faber-Castell, Rotring (600/800), Retro 51 Tornado, Tactile Turn, Karas Kustoms
Pilot / Namiki Cartridge
Length: 59.0 mm | Wide 5.5 mm bore | Capacity: ~0.90 ml (IC-50 / IC-100 / Parallel)
Lamy T10 Cartridge
Length: 68.0 mm | Stepped friction collar | Capacity: ~1.15 ml (Lamy Safari, 2000, Studio)
Sailor Proprietary Cartridge
Length: 48.0 mm | Flared ribbed collar | Capacity: ~1.00 ml (Sailor 1911, Pro Gear)
Platinum Proprietary Cartridge
Length: 65.0 mm | Metal stainless steel sealing ball | Capacity: ~1.20 ml (Century #3776, Preppy)
Parker Quink Cartridge
Length: 76.0 mm | Stepped friction plug with reserve tank | Capacity: ~1.20 ml
Cross Cartridge
Length: 38.0 mm | Narrow tapered mouth (Classic Century vs Townsend / Peerless)