I have the original TK1 folding trike and this battery fits perfectly and last a full day longer + for me. I take my puppy out 8 miles a day.
It comes attached to a mounting plate ( with wires )that you just slip off like you do if it was on the bike. No need to remove screws
Original battery charger that comes with the TK1 works the same.
The locking battery keys are differently keyed so you will need to keep those handy to lock and unlock the battery. I put colored tape on each key and each battery to differentiate which key goes to which battery.
You do not have to lock the batteries in place to use. It is just a good idea to secure it to the bike as they are not cheap.
Love the new battery and now I can always have one fully charged and ready to go.