Confirmed Fitment
STI Hi Cap Magazine Loader
The STI Hi Cap is confirmed to fit the Super Thumb ST2, the loader ADCO builds for wide-body double-stack magazines. It loads STI Hi Cap magazines faster and with far less thumb strain — a purpose-built tool, not a one-size-fits-all compromise.
Why loading these magazines is a fight
Double-stack magazines get progressively harder to load as the spring compresses — the top few rounds are where thumbs give out. The Super Thumb pushes each round straight down against that spring tension for you, so topping off to full capacity takes seconds instead of sore thumbs.
Your Fit
Super Thumb ST2
Wide Body Double-Stack
Width
1.5" (38.6 mm)
Height
1.01" (25.4 mm)
STI Hi Cap loader — common questions
Which Super Thumb fits the STI Hi Cap?
The STI Hi Cap is a confirmed fit for the Super Thumb ST2. It appears on ADCO’s verified Super Thumb fit chart as an exact match.
What kind of magazine does the Hi Cap use?
The Super Thumb ST2 is built for wide-body double-stack magazines, which is the class the STI Hi Cap uses.
Is the STI Hi Cap fit guaranteed?
Every Super Thumb is backed by a lifetime warranty. If you’re not certain, confirm with the Model Finder or call ADCO at 781-935-1799 before you order.
Not 100% sure? Confirm before you order.
Super Thumb loaders are model-specific. Use the Model Finder to double-check your exact firearm and magazine, or call ADCO Arms and we'll confirm the right loader for your STI Hi Cap. Every Super Thumb is backed by a lifetime warranty.