uni Jetstream Prime Twist-Action Single (Black): A Heavier, Better-Balanced Everyday Pen

Introduction

uni has refreshed the Jetstream Prime twist-action single, and the headline news for many buyers is the arrival of a full black version. Priced at 3,850 yen, the new model costs slightly more than the previous generation and gradually replaces it on the market. Dark navy and black are the two launch colors, with black shipping with a 0.7mm Jetstream refill and dark navy with a 0.5mm.

The Prime line sits at the premium end of uni’s Jetstream range, and this update leans noticeably more casual than older versions. Rounded edges and the all-black finish give it a more general-appeal look, moving away from the formal styling that has traditionally dominated higher-end ballpoint pens.

First Impressions and Build

The first thing you notice when picking it up is the weight. It is a genuinely substantial pen, which initially makes it feel heavier than expected. Measured against the previous model, though, the numbers tell a slightly different story: the old version weighs 30.4g and the new one 30.1g, so it is actually a touch lighter. The metal barrel and generous 10mm maximum diameter give it a stable, confident feel in hand.

The matte black coating feels smooth and slightly dry to the touch, without being slippery even for dry hands. The upper barrel is shorter than before, which shifts the balance point lower in the pen, and the twist mechanism retains the firm rotation of the old model, with a light locking sensation when the tip is fully extended.

The New Clip Design

The clip is one of the biggest visible changes. It is wider than before and uses a slit design with a small opening in the center. The finish is consistent across the black model, with a matte clip matching the matte body, which keeps the overall look clean. The clip is fairly stiff and slightly short, and the tip angles upward enough that it can just touch the hand while writing.

For the dark navy colorway, the clip is a matte silver, a pairing that divides opinion. On the black model the unified color makes the design fade into the background and read as intentional.

Writing Performance

The supplied refill is the SXR-60 0.7mm Jetstream, and it is the standard Jetstream rather than the Lite Touch variant. That difference matters: where Lite Touch can feel almost too slick, the standard 0.7mm delivers the familiar smooth, comfortable Jetstream glide with a bit more control.

The added barrel weight combines with that ink character to make writing feel easy and stable. Tip wobble, which was present on the previous generation, has been noticeably reduced on the new body, leaving only a trace of movement. The lower center of gravity is the most meaningful ergonomic change here, and it shows in steadier handwriting.

Things to Consider Before Buying

The refill situation is flexible. Although black launches with 0.7mm and dark navy with 0.5mm, either thickness can be swapped in later to suit your preference, since the initial refill is just the factory configuration. The refill uses the widely compatible G2 format, which is a practical advantage for long-term ownership.

There are a couple of trade-offs worth weighing. The slit clip design is the most polarizing element, and the slightly short, upward-angled tip can brush against your hand during longer writing sessions. Everything else, from the reduced tip wobble to the improved balance, points in the right direction.

Buying Advice

If you have been waiting for a black Prime, this is the version to get. The unified matte black finish, lower balance point, and smoother-tipped 0.7mm refill make it a comfortable daily writer with a modern look. If the slit clip bothers you, the previous generation remains the conservative choice, but as the old model is phased out, the new one is the natural default for the Prime lineup going forward.

Conclusion

The new Jetstream Prime twist-action single is an evolution rather than a redesign, and that suits it well. The all-black styling and improved weight balance are the standout improvements, while the clip design is the main point of contention. For anyone wanting a premium-feeling Jetstream in a color that goes with everything, it is an easy recommendation.