What is an STP?
An 'STP' or a 'stand-to-pee' device allows you to pee standing up.
STPs range from plastic non-realistic funnels to hyper-realistic silicone penises.
STPs can help curb gender dysphoria by enabling you to pee while standing, and also use public bathrooms, including the urinal.
Like packing, using an STP is not something that every trans / gender variant person chooses to do. It's totally up to you.