Best Compatible Refills for the Pilot FriXion Point Knock Biz and Ball Knock Zone

Introduction

The Pilot FriXion Point Knock Biz and FriXion Ball Knock Zone are attractive pens that ship with erasable ink by default. The good news is that both are compatible with a wide range of other refills, so if you like the look of these pens but prefer oil-based or water-based ink over erasable ink, you have real options.

Both pens use the C-300 type refill standard. However, because the pen mechanisms differ, not every C-300 refill fits both pens. It is perfectly normal for a refill to fit one but not the other. Also worth noting: even when a refill is compatible, long-term use could lead to issues, so proceed at your own risk. The refills below were tested in both pens for fit, writing feel, and tip stability.

Pilot Juice Up LP3RF

Pilot’s Juice Up is a natural first pick, since it uses the same Synergy Tip design as the Point Knock Biz. That tip combines the smoothness of a conical tip with the reliable start and durability of a needle tip, which is why so many people love how it writes.

The LP3RF series comes in 0.3, 0.4, and 0.5 mm tip sizes with four ink colors: black, red, blue, and blue-black. Tested in the Point Knock Biz, there is no wobble in the tip and the writing feel is great. In the Knock Zone it fits cleanly with no tip wobble either, and since it is the same Pilot brand, the whole experience feels very natural. It costs 132 yen including tax.

Uni Jetstream SXR Series

Uni’s most popular ink is, of course, Jetstream, and it works here too. Interestingly, it is not a C-300 type, so despite the different look, it actually fits perfectly. The SXR38, SXR5, SXR7, and SXR10 all work, with tip sizes of 0.38, 0.5, 0.7, and 1 mm, in black, red, and blue.

In both pens there is a slight wobble in the tip, but it does not affect the writing experience, which remains good. At 110 yen including tax, it is also one of the more affordable options.

Pentel EnerGel XLRN Series

Pentel’s gel ink refill of choice is EnerGel, and it comes in a huge variety of colors. The XLRN series covers XLRN3, XLRN4, XLRN5, XLRN7, and XLRN10, with tip sizes of 0.3, 0.4, 0.5, 0.7, and 1 mm. Sizes from 0.3 to 0.5 mm use a needle tip, while 0.7 mm and up use a conical tip. Colors vary by size, but black, red, blue, blue-black, and brown are available.

There is also the XLRN4TL, XLRN5TL, and XLRN7TL series, in 0.4, 0.5, and 0.7 mm. The 0.4 and 0.5 mm sizes have needle tips and the 0.7 mm version has a conical tip, with ten colors: black, red, burgundy, blue, blue-black, orange, dark gray, pink, turquoise, and violet.

One important catch: EnerGel only fits the Point Knock Biz and did not fit the Knock Zone. Tip wobble is a bit significant, so it is not recommended purely for the writing experience, but if you really want EnerGel ink in your FriXion, it is worth a try. It costs 99 yen including tax.

OHTO BNZK Suisei Gel

The OHTO BNZK series is not a C-series refill, but it works just fine. It comes in 0.5 mm only, in black and blue-black, using OHTO’s newly developed Suisei Gel, and it fits in both pens.

Both pens show a bit of tip wobble with it, but the wobble is well within a usable range. At 330 yen including tax it is the priciest option tested, but it is the only way to get Suisei Gel into these pens.

OHTO Zoom C1 BRZK Series

OHTO’s Zoom C1 ultra-low viscosity refill, the BRZK series, also fits both pens. It comes in 0.5 mm and 0.7 mm tip sizes and is available only in black.

Like the BNZK, it costs 330 yen including tax, so you can choose between Suisei and this one based on the ink character you prefer. Both use conical tips.

OHTO Rollerball C300 Series

The OHTO rollerball C300 series comes in 0.4, 0.5, 0.7, and 1.0 mm tip sizes, available in black, red, and blue.

This refill did not fit the Point Knock Biz, but it works in the Knock Zone. The catch is cosmetic: the tip sticks out quite a bit, so it does not look great. On the plus side, it retracts fully and there is no wobble at all, so it is fine to actually use.

Refills That Did Not Fit

Not every popular refill made the cut. Zebra Sarasa and Uni-ball refills unfortunately did not fit either pen. Many other C-series refills beyond the ones tested here may fit, so if you have a specific refill in mind, it is worth testing carefully before committing.

Buying Advice

The safest overall choice is the Pilot Juice Up LP3RF, which fits both pens with no tip wobble and the most natural feel. For affordable everyday ink, the Uni Jetstream SXR series is a solid pick despite minor wobble. EnerGel is only for Point Knock Biz owners who specifically want that ink. OHTO’s Suisei Gel and Zoom C1 are the options if you want a distinct ink character and accept a small amount of wobble, while the OHTO rollerball C300 is Knock Zone only, with the caveat of a visibly protruding tip.

Whatever you choose, remember that compatibility does not guarantee trouble-free long-term use, so treat these swaps as an informed experiment rather than a guaranteed upgrade.

Conclusion

The FriXion Point Knock Biz and Ball Knock Zone are far more flexible than their erasable-ink reputation suggests. Whether you want the refined feel of the Juice Up, the smooth Jetstream ink, the huge EnerGel color range, or OHTO’s distinctive gels, there is a compatible refill for most preferences. Match the refill to your pen model and your ink priorities, and these pens can become genuinely versatile daily writers.