In April each year Stockholm City bikes are back in their stands and ready to be used.
For a seasonal card (April - October) you pay SEK 250:- (2017) and have the use of a bike from 140 stations for 3 hours each time, Monday-Sunday from 6am to 10pm (but you can return the bike until 1am).
They even offer a free bike helmet if you make your way to their office:
Elektravägen 33, Västberga
week days between 07.30-16.00.
For more information check their website: