OK, here we go. the best way to know what size you need is to measure the gap. I personally like about 35mm and the gap in my S3 is 50mm so I have a 15. for 20 quid + 4 quid Postage, I'll make and send you two different sizes and the 5mm end plug. the 5mm hole is oversized so that it is tightened up against the opposite cap. they're switchable either side so there's the full range of adjustments. the inner part is slightly elliptical as my pedal wasn't round so it has a bit of adjustment in it. you may need to do a little bit of filing to get it to fit. I do black as standard, but for an extra £5 I can do orang, green, red and grey. please note that these won't fit the old style pedal that looks like this. if you have one of these tell me as I have a DIFFERENT version that will fit yours!
a video of my feet in my S3 chassis and a 15mm plug and here's a photo of my S3 pedal box with my 15mm: this is a 25mm in an SV chassis if you want a set go here: https://graearea.github.io/ I'll send them out and then pay me the cash when you're happy with the product. cheers! J