Foam surround replacement question

My woofers' (dynau 30w100) surround have rotted. I ordered a new set of foam surround from speakerbits, Australia. I just discovered that they didn't include the new dust caps. Is it ok to replace surrounds without replacing dust caps? Their instruction didn't mentioned anything about dust caps either.
I would recommend using the dust caps.Is it possible to use the "old" dust caps? You will notice a difference,if the caps aren't used.
The dust cap is sometimes the source of higher frequencies which the large cone cannot follow. Same idea as a "whizzer" cone. And then there is dust to worry about.

Better replace the dust caps.
The dust cap on the 30W100 is an integral part of the cone, or at least on mine it is. Also, the small indentations surrounding the 'dust cap' are there to locate the cone on the voice coil. You probably don't want to mess with that. I don 't know what your Speakerbits kit includes, but you may want to protect your investment by having them professionally reconed. The Dyn kit includes new foam, cone/dustcap, spider and voice coil - pretty much giving you a new speaker. Replacement is done with an alignment jig to keep the voice coil aligned in it's gap. Madisound did a pair for me. Not cheap, but then you did say Dynaudio.
Many thanks for all your kind responses.
Speakerbits has two versions of refoaming instruction. The instruction for 30w100 did not mention anything about voice coil shiming while the instruction for the 30w54 specified that shimming the voice coil is essential. I've emailed speakerbits about this but haven't got any reply yet. Any comments on this, please?