Im very new to higher powered rocketry, i grew up building the simple estes kits. Estes has their way of measuring tubes, BT55 etc. Some tubes are measured by inches some us metric (wouldnt it be nice if everything was metric?) I purchased a large box of someone's old rocket equipment and he had tubes of all different thickness, widths... also couplers, bulkheads, thrust rings... lots of stuff! i have a digital measuring tool and try to see what is what, or what i need to buy to fit this and that. I see 29mm, 1.1"/1.1"(P)/ 1.1"(S).. so many different ways of describing its measurements. Is there a document that makes sense of all this? Like in a way a 5 year old could understand haha thanks!!!