Which RefillPen Is Right for You? V1 vs V2 vs V2.5 vs V3

All four RefillPen pens run on the same standard 3mL glass cartridge and universal pen needles, dial one click per unit, and are fully reusable - you only ever replace the cartridge, never the pen. The real differences are cap style, dose range, and feel. Here is how to choose.

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V1 (Closed Cap) - the widest dose range. Machined from solid aluminum with an 80-unit range, the most in the lineup. Its closed cap means you see the needle as you inject. Best for experienced users who want the largest dose range.

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V2.5 Slim Hybrid (Open Cap) - the most comfortable. The slimmest, lightest body with a 60-unit range and a hidden-needle open cap. Best for anyone who wants the easiest, most comfortable pen to hold and use.

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V2 (Open Cap) - the open-cap classic. Its open cap keeps the needle out of sight while you inject; 60-unit range in solid aluminum. Best for the open-cap feel at our best price.

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V3 (Closed Cap) - the slim closed-cap. The V1-style slim body with a 60-unit range and a closed cap, so you see the needle as you inject. Best for closed-cap users who prefer a slimmer pen.

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How to choose: closed cap (V1, V3) means you see the needle - the setup many experienced users prefer; open cap (V2, V2.5) keeps it hidden. Want the biggest dose range? Choose the V1 (80 units). Want the most comfortable pen? Choose the V2.5. Every pen refills for about $1 a cartridge. For research purposes only.