it started with dick. he was barely double digits when he came into the role, and so bruce only let him out on cases where it was investigative with minimal (if any) fighting. he didn't need the armour or the protection, so bruce let him have (mostly) free reign of designing his costume. then everything happens and dick leaves his role as robin. but during his time, bruce would notice how his knees and elbows ran a hot, angry red after each patrol. even if no actual fighting occurred, the cold or the climbing and parkouring rooftop to rooftop was starting to wear the skin of his knees down. and when this fighting did happen, bruce noticed his elbows taking most of the blunders.

to be fair, toward the end dick was fighting more and it scared bruce, but, dick was gone before he could start developing the robin suit to be more suited to vigilantism. bruce swore up and down that he would never have another robin after dick, but on nights where he'd read a new case file about a villain he and dick had fought, or he hears news of what's happening in bludhaven, he starts to design more advanced versions of the robin suit. its nothing incredible, the changes are minimal, but he figures if dick was to ever come back to him and abandon nightwing, he would be prepared.

then came Jason who was older, more experienced in life by this point, and had a thirst for justice. bruce knew he couldn't gradually introduced Jason in like he had dick so he bought himself time in developing Jason's suit for months and months until he got to a point where a) Jason was getting too ansty and it could be dangerous and b) he had nothing left to change. and so he revealed this new robin suit designed with the nuance he had from dicks experiences (and the many scenarios that kept him up at night about everything that could go wrong).

first, it was the kneepads. and elbow pads (think this). they were designed to take the impact of most damage robin could face, reinforced with the newest weave of kevlar surrounding the thin carbon fibre plates. then, the shoes. the soles were fitted with extra-durable material that was extra-lightweight for little Jason, not to mention the emergency button within the sole itself, settled right next to slight tracks so he could manoeuvre in any terrain. his gloves had the same heat and ice protections as the top and shorts that proved useful if he ever got into, say...an explosion of some sort.

Jason loved it, but, just like with dick: things don't last forever. to be fair, he was mostly forced out of that role entirely by unsuspecting circumstances, but it only gave bruce more material.

again, he hadn't planned on another robin, but some part of him was almost comforted by making new alterations to the old robin suits. on the other hand, it worked as a sort of self harm for him--near torturing himself going back over what he could've done differently. what more he could've done.

then came Tim. his first ever robin outing was dressed in an earlier jaybin costume than the one he died in (without the knee and elbow pads--this scared bruce immensely the first time he saw it). bruce, driving home semi delirious with discowing on one side, this new (strange?) kid dressed head to toe in his dead sons uniform and Alfred in the front after an encounter gone wrong with Harvey (read: a lonely place of dying) was doing his head in. but not as much as this new kid, dick, and Alfred were about hiring the kid to be the new robin.

to his dismay and better judgement, bruce did. this time, the robin uniform had full coverage, save for the arms, with that same heat and ice protection, kevlar was weaved into any area he could find, and metal plates reinforced the body's most important areas. hardened gauntlets connected into uber protective elbow pads, leaving minimal space open only so that, if need be, Tim could rip the suit of at a moments notice. too bad Tim stopped being robin for a time because bruce was (somewhat) okay with the protections in that version of the costume. then

there was Steph.

bruce isn't dumb. he knows the dangers of being a) a person in Gotham, b) a vigilante in Gotham, c) a woman in Gotham, and d) a woman vigilante in Gotham. so, with some stylistic changes for her in the form of a longer top, a bright red headband, and a matching set of hair bands his design upgrades largely revolve around this. the headband is fitted with a tracking device and the hairbands are reinforced to hold her entire body weight and then maybe bruce, as well. just in case.

her domino is updated, too. the lenses, fitted with a recording device now has an audio option (somehow). the buckle of her belt is fitted to shock anyone at a moments notice, and, the tips of her gloves can be rubbed together to produce another electric shock, in case she can't reach the buckle. Stephanie 100% uses this on Tim later. the tips of her boots are reinforced with steel. and, most importantly, the the big robin 'R' on her chest actives an immediate alarm straight to bruce, Alfred, the batcave, or whoever is covering for any one of them. that, too, is fitted with an audio recording feature, just in case.

bruce is particularly proud of the advancements he's made on steph's suit. he feels relatively comfortable letting her out to robin every night, but it's not enough. their differences, her not listening, and his fears get the best of them and her brand new suit barely gets worn in.

when Damian arrives, bruce adopts a lot of Steph's design into his own (save for the headband and hairbands). there aren't a lot of changes to the function of the suit, but one thing he finally puts in is full sleeves. bruce remembers, even back with dick, how the robins all used to wrap their capes around themselves for warmth. he figured movement was a greater pro than the con of sometimes getting cold. but now? bruce installs longer sleeves that are made up of carefully weaved plates of thin metal encased in kevlar. they're so small, so lightweight, that Damian actually doesn't notice until bruce allows him creative direction for some design changes.