... and why did they make them so weird? I fitted new seals & holders a couple few months ago and for various reasons have only just got back in the shed only to discover that oil was weeping past the threads on one of the seal holders as I hadn't sealed it properly. The fact I had to dismantle the whole lot, including getting that pesky circlip out, then reassembling it, made me wonder why on earth someone designed the stanchions with multiple diameters so you can't just slide the seal over the top end like Norton etc with a single diameter stanchion. Surely it was more expensive to make the BSA pattern with different diameters as there's lots more machining?
Plus why not just screw the seal holder into the inside of the slider rather than the outside, again like Nortons, so it would hold the top bush in place? Quite apart from avoiding aforesaid circlip, there again is less machining and it's so much easier to put together.
Perhaps it's something to do with patents but the actual working bits - bushes, damping mechanism, hydraulic stop etc - are very similar between the two marques.
Sorry if I've offended died in the wool BSA people....