Bung:
Centra Windows are a Canadian company, Robertson screws are a Canadian invention. How many square drive bits are in your Ryobi kit? There are 5 sizes in the Robertson range #00, #0, #1,#2 & #3. Most kits might have 1,2 &3 and I've only ever needed the #2.
yes you are right. I have five pieces, oddly labelled. 2 are S2 and measure 3mm, the largest is labelled s1, i forget the next 2. but the smallest one measures 2mm exactly. I think we have cracked the case sherlock.
Still not happy having 2 pieces the same size, i cannot see with my eyes any notable difference.
So I presume #2 relates to 2mm?

