In physical size they are but capacity is different. I think the R50's are 300's and the R53 are 330's with JCW's being 380's.
Just a quick run through realoem.com, confirming that they are different parts... For a mid-2005 build R50: Injector part # 13531487607 ($107.12) For a mid-2005 build R53 up to 7/2007: Injector part # (up to 7/2007) 13531521390 ($107.12) For a mid-2006 build JCW up to 7/2007: Injector part # 13530391511 ($126.95)
= + 2 There have been many updates on many part numbers over the years. realoem is not the best definitive information source for part #S According to a few BMW/MINI dealerships the better part source is
We also have two great site sponsors that are dealer based OEM Parts operations. IMBMparts.com and OEM Mini Accessories & Replacement Parts Warehouse Even if you grab a superseded part number from RealOEM and plug it in on these sites you will get the latest version of the part when ordered.