Energy with more behind it
Berserker Stim combines high caffeine with carbohydrates, pump ingredients, and focus support for demanding sessions.
THE COMPLETE STACK3 full-size products
Made for your routine
Experienced adult lifters who want options across demanding strength sessions, focus-heavy workouts, and days when they prefer no added caffeine.
Explore every product
BUILT AROUND YOUR GOALS
More control over your pre-workout routine.
A different kind of focus
Berserker Focus is the caffeinated, focus-first alternative. Choose it instead of the other stimulant formula when it better fits your session.
A liquid option without added caffeine
Berserker Serum brings glycerol and citrulline in a measured liquid format. It gives you another approach to your pump routine.
EVERY PRODUCT HAS A JOB
Here’s what arrives.
One full-size container of every product below. Explore the individual pages for complete formulas, labels, and directions.
01ENERGY + PUMP + TRAINING FUEL
Berserker Stim™ Pre-Workout
1–2 scoops per workoutHigh caffeine with carbohydrates, substantial pump ingredients, and tyrosine for demanding training.
- 1 full-size tub
- Standalone price: $59.99
- Supply at the stated serving
- 40 one-scoop or 20 two-scoop workouts
How and when to use it
Take before training. Start with 1 scoop; follow the label and your tolerance. Two scoops contain 400mg caffeine anhydrous plus additional caffeine from Infinergy. Do not combine with other caffeine or stimulants.
02CAFFEINATED FOCUS FORMULA
Berserker Focus
20 full-scoop workoutsA focus-first pre-workout for the sessions that demand your attention as much as your effort.
- 1 full-size tub
- Standalone price: $39.99
- Supply at the stated serving
- 20 full scoops or 40 half scoops
How and when to use it
Experienced users: 1 scoop in 10–12 oz of water before training. New users: start with ½ scoop as directed on the label. Avoid close to bedtime and do not combine with other caffeine or stimulants.
03LIQUID PUMP FORMULA
Berserker Serum
1–2 capfulsActive glycerol and citrulline in a liquid formula with no added caffeine.
- 1 full-size bottle
- Standalone price: $59.99
- Supply at the stated serving
- 50 one-capful or 25 two-capful servings
How and when to use it
For training, measure 1–2 full capfuls (20–40mL), following the bottle’s directions. Start with 1 capful and drink adequate water. Review overlapping focus ingredients before combining products.
MAKE YOUR CHOICE COUNT
Full-size formulas. One clear plan.
Buying the line together gives you three distinct tools at a bundle price. You keep the original formulas, serving flexibility, and product-level ingredient details, with one set of flavor selections and one order.
FROM PEOPLE WHO USE THE PRODUCTS
The products. Their experience.
Selected excerpts from customer reviews of products included in this stack. These are product reviews, not reviews of the complete bundle.
Review of Berserker Focus
Read the full product reviews10/10 for workouts and for study/deep work.
Review of Berserker Serum
Read the full product reviewsThis stuff absolutely blew me away the first time I tried it and never experienced a pump like this ever and I was just locked in all session.
Selected customer reviews. Individual experiences and results vary.
When to use it
Make it part of your day.
PLAN THE SESSION
Pick one caffeinated formula
Choose Berserker Stim or Berserker Focus. Do not take them together or combine them with other caffeine or stimulants.
CAFFEINE-FREE OPTION
Measure the liquid serving
Use Berserker Serum according to its bottle directions, starting with 1 capful. Drink adequate water and review its other active ingredients.
MAKE IT FIT
Protect the rest of your day
Avoid caffeinated products close to bedtime. Serum and the powders share some focus ingredients; review the full formulas before considering a combination.
These steps organize the products by role. Follow each label and your individual guidance; buying a bundle is not an instruction to take all products together.
FOUNDER LED. PERSONALLY ACCOUNTABLE.
Built by someone who knows both sides.
Before building Hollow Labs, Allen Collins owned supplement stores. The questions customers asked then still shape the brand: what’s in it, how much do I take, and why is it worth buying?
We put the formulas where you can inspect them, explain where each product fits, and stay reachable when you need an answer.
What Hollow stands forHOLLOW LABSSEEK ADVERSITY.Ask the Hollow team
What exactly will I receive?
You receive one full-size retail container of every product shown in “What’s included.” Choose from the flavor options available above before adding the stack to your cart.
Will the whole stack last the same amount of time?
Not necessarily. Containers have different serving counts, and daily products can run out sooner than products used only for selected workouts. Each product card shows its supply at the stated serving.
Can I choose my flavors or swap products?
Choose the available flavor options in the selectors above. The products in each stack are fixed; open an individual product page if you prefer to build a different order.
Can I combine the two powders?
No. Berserker Stim and Berserker Focus are both caffeinated stimulant formulas. Choose one for a session and avoid other caffeine or stimulant products.
Does no added caffeine mean Serum has no other actives?
No. Berserker Serum contains additional active ingredients, including vinpocetine and a huperzia ingredient. Review the full label and overlapping ingredients before combining it with a powder.
Is this stack for every lifter?
It is built for experienced adults who tolerate stimulant formulas and want to choose between them. Berserker Serum must not be used during pregnancy or if you could become pregnant. Review suitability with a healthcare professional.
How do shipping and returns work?
Free shipping applies to orders of $75+ after discounts, with eligibility confirmed at checkout. See our return policy for the 30-day return process and terms.
MATCH THE ROUTINE TO YOUR GOAL
Choose the stack that fits.
Cover more of your week
Hybrid Athlete Stack
A broader routine for lifting, endurance, and recovery habits.
ENERGY. FOCUS. LIQUID PUMPS.
Choose your formula. Show up ready.
Choose your stack optionsFull-size products. Current bundle price. One order.
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.
