SWISS bids are direct 4 or 4 jumps over an opening of 1 or 1

These SWISS bids show Balanced hands & (15)16+ HCP with good 45 major support.
If a SWISS bid is made following an opponent's intervention then there can be a shortage in the opponents bid or implied suit.
SWISS bids are not SPLINTERS! Splinters which are not used in this system over Opening bids.

Note: However Splinters are used over a  1-level suit response. E.g. 1-1-4...

The difference between 4 & 4 is:

4 promises EXCEPTIONAL trump support usually 7 HCP in the trump suit.
This would reassure an opener who is concerned about the honour strength he holds in his suit - who might well otherwise not attempt a slam.