One Stop Xtreme Powder
by Reflex Nutrition
Calories that count: a high-protein, high-carb formula built for serious muscle and weight gain.
- Up to 34g protein per serving
- High calorie for bulking phases
- For shakes, smoothies, baking and more
Flavour pictures illustrate the taste, not the powder's colour or ingredients.
Best price today
In stock£70.56
£1.62 / 100g
Secure retailer checkout
We may earn a commission at no extra cost to you. Affiliate disclosure
Transparent protein profile
What's inside
Values per 100g, with the amount in one 76g serving
45g protein
34.2g per 76g serving
35g carbohydrates
26.6g per 76g serving
8g fat
6.1g per 76g serving - moderate fat
400 kcal
304 kcal per 76g serving
View full nutritional information
| Nutrient | Per 100g | Per serving (76g) |
|---|---|---|
| Protein | 45g | 34.2g |
| Calories | 400 kcal | 304 kcal |
| Carbohydrates | 35g | 26.6g |
| Fat | 8g | 6.1g |
Know when to buy
Price history
Lowest price on record, any flavour or size
£1.07/100g (£46.49 for 4.35kg on 24 Sept 2026)
4.35kg · all flavours · price per pack
- Amazon UKlatest £70.56, lowest £46.49, highest £74.75 in the last 90 days
Quick answers
Is this right for you?
Who is it for?
Reflex Nutrition One Stop Xtreme Powder is designed for hard-gainers and anyone in a dedicated bulking phase who struggles to eat enough calories. Mass gainers combine protein with carbs and calories to support weight gain and muscle growth during intense training blocks.
What can you expect?
A calorie-dense shake designed to help you gain weight. Mass gainers pack protein alongside a significant amount of carbohydrates and calories per serving. Servings tend to be larger than standard protein powders, so expect thicker shakes and bigger scoops. With 45g of protein per 100g (around 34g per 76g serving), Reflex Nutrition One Stop Xtreme Powder sits in a competitive position for a mass gainer product.
What else do you need to know?
Reflex Nutrition One Stop Xtreme Powder is a mass gainer protein powder made by Reflex Nutrition. It comes in 2.03kg, 4.35kg sizes. Every price on WheyWise is read from the retailer’s own page and re-checked daily and sorted by cost per 100g, so you can see both the cheapest option and how current it is. All links to Amazon and retailer sites are affiliate links - this is how WheyWise stays free.
Frequently asked questions
Where is the cheapest place to buy Reflex Nutrition One Stop Xtreme Powder in the UK?
We refresh Reflex Nutrition One Stop Xtreme Powder pricing daily from Amazon UK and show the fetch time next to every figure. If no verified price is showing above, we do not currently hold one we would stand behind, and the buy button will take you to the live listing to check.
How much protein does One Stop Xtreme Powder contain per 100g?
One Stop Xtreme Powder contains 45g of protein per 100g, with 34.2g per 76g serving. It is a mass gainer product.
Is Reflex Nutrition One Stop Xtreme Powder currently in stock?
At the last check, 18 out of 18 tracked variants were in stock. Stock status carries the same fetch time as the price shown above, so check the retailer listing before ordering.
Pick your pack
2 sizes · Vanilla · cost per 100g for each
The 4.35kg works out at £1.27 per 100g. The 2.03kg costs £1.87. Same powder, 1.5x the price per gram.
Where to buy in the UK
Vanilla · 4.35kg · 1 offer for this selection · sorted by cost per 100g
Similar products you might prefer
Other mass gainer powders from different brands, cheapest per 100g first.
The Bulk Protein Company
Vegan Gainz
Applied Nutrition
Critical Mass Professional Lean Mass Gainer
Medi-Evil Nutrition
Purely MASS - Special Offer