A measured liquid format
One capful is 20mL. Two capfuls is 40mL. These are liquid capfuls, not capsules.
Made for your routine
Serious lifters who want a liquid pump formula, especially when limiting caffeine or training later.
Explore the formula ↗
What you can expect
A reason behind the formula.
Bring active glycerol and citrulline into a pump-focused session without another dose of caffeine. Focus ingredients round out the liquid formula.
Glycerol plus citrulline
At one capful, you get 10g active glycerol and 5g L-citrulline.
Keep caffeine separate
No added caffeine gives you another way to build a pre-training routine.
Inside the formula
The amounts matter.
Per 1–2 capfuls (20–40mL)
100% active glycerol
1–2 capfuls, respectively.
L-citrulline
1–2 capfuls, respectively.
Agmatine sulfate
Alongside betaine and taurine.
L-tyrosine
Part of the focus formula.
Alpha GPC
The formula also contains other choline sources, vinpocetine, and huperzine A; read the full label.
View the full Supplement Facts
Amounts shown in the highlights use the serving basis above. The original label includes the complete panel, other ingredients, and allergen information.
Open the full-size label ↗
Why choose this formula?
Make your choice count.
Serum’s distinction is its liquid format and explicitly labeled active glycerol. Glycerol powder ingredient weights do not automatically equal the same amount of active glycerol.
| Consideration | Your priority | What you get |
|---|---|---|
| One capful | 20mL | 10g active glycerol + 5g citrulline |
| Two capfuls | 40mL | 20g active glycerol + 10g citrulline |
| Bottle value | Choose your serving | 50 smaller servings or 25 larger servings |
Your supply50 one-capful or 25 two-capful servings
Choose your option ↗Your routine
Make it part of the plan.
Measure 1–2 full capfuls (20–40mL), following the bottle’s directions. Start with 1 capful to assess your response and drink adequate water. Do not exceed the label’s maximum serving.
The Hollow standard
Built for people who put in the work.
Before building Hollow Labs, Allen Collins owned supplement stores. The questions he heard from customers still shape the brand: what is in it, how much do I take, and why should I choose it?
Our standard is simple: make the formula easy to understand, explain where it fits, and stay reachable when you have questions.
Meet Hollow Labs ↗HOLLOW LABSSTANDARDS BEFORE SHORTCUTS.Ask our team ↗
Do you mean capsules?
No. Serum is a liquid. Use the bottle cap to measure 1–2 full capfuls, equal to 20–40mL.
Can I stack it with a stimulant pre-workout?
No added caffeine does not make every combination suitable. Serum has a substantial focus formula; review overlapping ingredients, especially huperzine A and choline sources, before combining.
How long does a bottle last?
It contains 50 one-capful servings or 25 two-capful servings. Your workout frequency determines how many weeks it lasts.
Before you use it
Contains vinpocetine: do not use during pregnancy or if you could become pregnant. Consult a healthcare professional before use with medication or a medical condition. Avoid duplicating huperzine A across products.
Returns policy
LIQUID PUMP + FOCUS
Measure your serving. Own your session.
50 one-capful or 25 two-capful servings
Choose your option ↗Free shipping on orders $75+ after discounts*
*Final eligibility is confirmed at checkout.
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.
FREE SHIPPING ON ALL ORDERS OVER $75
FROM THE JOURNAL
Know what goes in your routine.
Understand the ingredients, read the label, and choose what fits your training.
