Had it confirmed now with Bilstein themselves, there is variations of the B4 and they are essentially the same item, though there is dimensional differences.
Using a standard B4 shock with effectively stock sport springs (~30mm lower than standard) will result in the shock wearing out faster. So, for standard height use B4 model 16-031319 and if on sport springs 21-030444 is the one you want.
Failing that get a B6 as previously mentioned
