yes they are. a little background.
I have a 15A compressor that I run off a 20A circuit if I plug directly into the wall it'll run no problem. but I needed extra outlets at that location. When I run the compressor that is the only thing I run at the time, but I like to have extra outlets available so I can plug in a fan, lights and vacuum. First thing I tried was some cheap power strip I had laying around with a 15A breaker, this ran fine for a couple of years but then it started to trip if the compressor was run for extended periods. So I went out and got one of these.
https://www.amazon.com/gp/product/B000FDAOEO/ref=s9_simh_gw_g60_i1_r?ie=UTF8&fpl=fresh&pf_rd_m=ATVPDKIKX0DER&pf_rd_s=&pf_rd_r=YW05R2MEVZ2EEZ921R8P&pf_rd_t=36701&pf_rd_p=6aad23bd-3035-4a40-b691-0eefb1a18396&pf_rd_i=desktop
this did not work and would also trip before even completing one refill cycle. I was thinking that this was a heavy duty strip made for the garage so it would holdup well, but no it can't.
so, I recently purchased this
https://www.amazon.com/gp/product/B000L4D3UO/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
granted its a 20A strip but it works perfectly and has not tripped once. I think those 15A units have breakers that react very quickly and trip to easily, they are not made for heavy duty use with constant loads from motors. I say plunk down your cash and get a tripp lite brand strip, they are well made not plastic junk. For $56 you don't even get any surge protection or other fancy features but you do get quality construction with quality parts.