Ré HV probes, there's a x100 tektronix but yes P6013/6015 are tge industry standard for HV work.
The P6015 uses a banned Freon as insulation, with no gas, the 40kV rating reduces to 15..20 kV.
The current version ( $$$) 40 kV Tektronix is P6015A, no freon , much smaller compensation box,
The main drawback of these enormous probes is indeed their size. We use tie wraps or tape to fix the probes on the DUT.
Instead, for my work 400..600 V like tube amps, mains, SMPS offline these old P6006..6009 are ideal.
Happy probing!
Jon