The ECO is the most affordable model yet from TWSBI. This pen features a piston mechanism, a clear barrel, clear cap and piston knob. The nib is smooth with a little feedback. The barrel is clear and smooth, which has lesser grip than a typical pen. Overall, it feels great holding in hand.

• Body Color: Serpentine
• Body Material: Resin
• Cap Type: Screw-cap
• Compatible inks & refills: Bottled inks
• Filling Mechanism: Piston
• Nib Material: Steel
• Diameter: 0.5″
• Length: 5.2″
• Max Ink Capacity: 1.76ml
• Release Date: June 25th, 2025

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About TWSBI:

TWSBI (San Wen Tong) is one of our earliest collection even before the store. TWSBI started as an OEM manufacturer for different western brands, and around 2009, they decided to start their own brand. With 50 years of experience in pen making, they took to fountain pen forums and gather users feedback. It was said that Pelican M800 was the model they were inspired. Most of their pens are transparent, so its really fun to see the ink color and it lasts for a very long time.

The name (San Wen Tong) comes from the Hall of the Three Rare Treasures, created by Emperor Qianlong as a memorial to three great masterpieces of Chinese calligraphy. The initials of the name San Wen Tong was reversed and thus turned into “TWS”. The last letters “Bi” was added with its literal meaning of “writing instruments” in Chinese. Thus combining the two segments, creating TWSBI.