Activate Shaker vs. Vitalize Shaker: what's the actual difference?

Both are 20 oz shaker-format Stanley bottles with an agitator ball and a flip-open lid. The Activate Shaker is the original format with a wider base and carry loop. The Vitalize Shaker has a slightly slimmer profile and a revised lid mechanism that seals more flush. Functionally both work equally well for protein shakes; the choice comes down to grip preference and which colourway you want.

Does the Stanley shaker keep contents cold or just mix them?

The Stanley shaker uses the same double-wall vacuum insulation as Stanley's tumbler range, so it keeps contents cold for several hours after mixing, unlike a basic plastic shaker that warms to room temperature in under an hour. In Indian summer heat (35 to 40°C), expect cold contents for 2 to 3 hours post-mix if the bottle was pre-chilled. This is the practical reason to choose Stanley over a standard gym shaker.

Does the agitator ball work with Indian protein powders that clump in water?

The stainless steel agitator ball handles standard whey and plant-based powders without issue. Casein and mass gainer powders, which clump more heavily, mix better if you add liquid first and then powder. If your protein is particularly thick, a short shake with the lid fully closed before inverting works better than shaking upright. The 20 oz capacity is sized for one standard 30 g scoop with 300 to 350 ml liquid.