I use a mixture of Gardena and Hozelock components.

I am currently looking at Gardena Reducing T-joint 13mm to 4mm

I have previously used the 4mm spurs which screwed in to the wall of
the 13mm pipe - and of course they are now leaking - I think they were
Hozelock Micro Irrigation Tube Adaptor / Connector (4mm) - 2778.

The Gardena ones do not look as if they are necessarily a good water
tight fit - the pictures seem to show a rubber ring washer around the
plastic pipe

Any comments, suggestions - or cheap but good look-alikes?